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IC 8849 



Bureau of Mines Information Circular/1981 




Room and Pillar Retreat Mining 

A Manual for the Coal Industry 



By Peter W. Kauffman, Steven A. Hawkins, 
and Robert R. Thompson 




UNITED STATES DEPARTMENT OF THE INTERIOR 



Information Circular 8849 



Room and Pillar Retreat Mining 

A Manual for the Coal Industry 



By Peter W. Kauffman, Steven A. Hawkins, 
and Robert R. Thompson 




UNITED STATES DEPARTMENT OF THE INTERIOR 
James G. Watt, Secretary 

BUREAU OF MINES 




As the Nation's principal conservation agency, the Department of the Interior 
has responsibility for most of our nationally owned public lands and natural 
resources. This includes fostering the wisest use of our land and water re- 
sources, protecting our fish and wildlife, preserving the environmental and 
cultural values of our national parks and historical places, and providing for 
the enjoyment of life through outdoor recreation. The Department assesses 
our energy and mineral resources and works to assure that their development is 
in the best interests of all our people. The Department also has a major re- 
sponsibility for American Indian reservation communities and for people who 
live in Island Territories under U.S. administration. 



/V^r 



3C- W, /W 



This publication has been cataloged as follows: 



Kauffman, Peter W 

Room and pillar retreat mining; a manual for the coal 
industry. 

(Information circular - Bureau of Mines ; 8849) 

Bibliography. 

Supt. of Docs, no.: I 28.27:8849. 

1. Coal mines and mining— Handbooks, manuals, etc. 2. Pillaring 
(Mining)— Handbooks, manuals, etc. I. Hawkins, Steven A., joint au- 
thor. II. Thompson, Robert R., joint author. HI. Title. IV. Series: 
United States. Bureau of Mines. Information circular ; 8849« 

TN295.U4 [TN800] 622s [622'. 334] 80-620000 



For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 



PREFACE 



This guidebook was prepared by Management Engineers Incorporated (MEI) , 
Reston, Va., under Bureau of Mines contract HO282021. The contract was 
administered under the technical direction of the Spokane Research Center. 
Mr. Robert Thompson was the Technical Project Officer; Mr. David Askins was 
the Contract Administrator. Mr. Peter Kauffman acted as Project Director. 
Mr. Steven Hawkins was Project Manager. 

This guidebook is the primary product from work completed under this 
contract during the period from September 14, 1978, to March 15, 1980. A 
final report detailing the conduct of the project was published under 
separate cover. The authors thank the many contributors to this project, 
including MSHA district and subdistrict managers and roof control special- 
ists, equipment manufacturers, and mining companies. Particularly the 
authors thank the participating mining companies who gave generously of their 
time in discussions and in underground visits. 

The authors also thank their consultants, Mr. Adler Spotte, Mr. Dewitt 
Foust, Mr. James Biller, Mr. Francis Martino, and Mr. John Pio, whose careful 
reading and critique added immeasurably to the final product. 

Contributing to this project from MEI were Mr. Daniel Walton, Mr. William 
Ingham, Mr. Svend Rondum, Mr. George Little, and Ms. Patricia Webb. Clerical 
support was provided by Ms. Cathy Mack, Ms. Sandra Hoybach, and Ms. Patricia 
Naughton. 



CONTENTS 

PAGE 

Abstract 1 

Chapter 1. - Introduction 1 

Chapter 2. - Summary and comparison of mining techniques. ... 2 

Pillar extraction processess 2 

Methods of mining production panels 12 

Chapter 3. - Regional retreat mining practices 18 

MSHA District 2 18 

MSHA District 3 20 

MSHA District 4 20 

MSHA District 5 21 

MSHA District 6 21 

MSHA District 7 21 

MSHA District 8 22 

MSHA District 9 23 

MSHA District 10 23 

Summary 23 

Chapter 4. - The basic pillar extraction processes 25 

Split and fender 25 

Pocket and wing 41 

Outside lifts 53 

Open ending 59 

Chapter 5. - Basic retreat methods of panel development and 

extraction 71 

Full panel extracted on retreat 71 

Rooms driven and extracted on retreat 87 

Rooms driven and extracted on both advance 

and retreat 96 

Chapter 6. - Mine planning and retreat mining 110 

Making the decision to retreat mine 110 

Mine planning for retreat mining 120 

Chapter 7. - Section operations 135 

Mining operations 135 

Roof support operations 138 

Section ventilation 139 

Planning for and moving supplies on section 141 



li 



PAGE 

Chapter 8. - The effects of the Coal Mine Health and 

Safety Act on retreat mining 147 

Roof control and ventilation plans 147 

Roof support 147 

Ventilation 150 

Electricity 155 

Chapter 9. - Developing a section foreman's guidebook 157 

Introduction 157 

Purpose of guidebooks 156 

Introducing the guidebook concept to foremen 156 

Developing the guidebook outline 157 

Selecting the format of the guidebook 158 

Assembling the information 159 

Improving and updating the guidebook 159 

Annotated bibliography 160 

Appendix. - Retreat mining practices 176 



ILLUSTRATIONS 

PAGE 

1. Split-and-fender cutting sequence 3 

2. Pocket-and-wing cutting sequence 4 

3. Outside-lift cutting sequence 5 

4. Open-ending cutting sequence 5 

5. Multiple splits 6 

6. Christmas-treeing cutting sequence (one pillar) 8 

7. Christmas-treeing cutting sequence (two pillars) .... 8 

8. Indicator-stump cutting sequence 9 

9. Fender -break through cutting sequence 9 

10. Fender-notching cutting sequence 10 

11. Split-and-fender cutting sequence using 

conventional mining equipment 10 

12. Nonsequential-pocket-and-wing cutting sequence 11 

13. Cutting sequence for outside-lift Christmas treeing. . . 12 

14. Full panel extracted on retreat 13 

15. Rooms driven and extracted on retreat 14 



in 



PAGE 

16. Rooms driven and extracted on advance and on retreat . . 15 

17. Rooms only 16 

18. Coal mine health and safety districts 19 

19. Split-and-f ender overall cut sequence 26 

20. Split-and-fender cut 1 27 

21. Split-and-fender cut 1 - alternate ventilation 28 

22. Split-and-fender cuts 2, 4, and 6 29 

23. Split-and-fender cuts 3, 5, and 7. . . 30 

24. Split-and-fender cut 8 31 

25. Split-and-fender cuts 9-11 32 

26. Split-and-fender cuts 12-14 33 

27. Split-and-fender cut 15 34 

28. Split-and-fender cut 16 35 

29. Split-and-fender cut 17-20 36 

30. Split-and-fender cuts 21-23 37 

31. Split-and-fender cut 24 38 

32. Split-and-fender alternate cut 24 39 

33. Pocket-and-wing overall cut sequence 42 

34. Pocket-and-wing cut 1 43 

35. Pocket-and-wing cuts 2 and 4 44 

36. Pocket-and-wing cuts 3 and 5 45 

37. Pocket-and-wing cuts 6, 1, and 8 46 

38. Pocket-and-wing cut 9 47 

39. Pocket-and-wing cuts 10-12 48 

40. Pocket-and-wing cuts 13 and 14 49 

41. Pocket-and-wing cut 15 50 

42. Pocket-and-wing alternate cut 15 51 

43. Outside lifts overall cut sequence 54 

44. Outside lifts cut 1 55 

45. Outside lifts cuts 2 and 3 56 

46. Outside lifts cut 4 57 

47. Outside lifts alternate cut 4 58 

48. Open-ending overall cut sequence 60 

49. Open ending cut 1 61 



IV 



PAGE 

50. Open ending cuts 2-6 62 

51. Open ending cut 7 63 

52. Open ending cuts 8-10 64 

53. Open ending cut 11 65 

54. Open ending cuts 12-14 66 

55. Open ending cuts 15 and 16 67 

56. Open ending cut 17 68 

57. Open ending alternate cut 17 69 

58. Full extraction on retreat panel development 72 

59. Full extraction on retreat bleeder connection 73 

60. Full extraction on retreat first pillar row 74 

61. Full extraction on retreat typical pillar row 75 

62. Full extraction on retreat pillar 1 76 

63. Full extraction on retreat pillar 2 77 

64. Full extraction on retreat pillar 2 (alternative) .... 78 

65. Full extraction on retreat pillar 3 79 

66. Full extraction on retreat pillar 4 80 

67. Full extraction on retreat pillar 5 81 

68. Full extraction on retreat pillar 6 82 

69. Full extraction on retreat pillar 7 83 

70. Full extraction on retreat belt move 84 

71. Full extraction on retreat conventional mining 85 

72. Full extraction on retreat continuous haulage 86 

73. Full extraction on retreat overall pillar sequence. ... 88 

74. Rooms extracted on retreat pillar 1 89 

75. Rooms extracted on retreat pillar 2 90 

76. Rooms extracted on retreat pillar 3 91 

77. Rooms extracted on retreat pillar 4 92 

78. Rooms extracted on retreat pillar 5 93 

79. Rooms extracted on retreat pillar 6 94 

80. Full panel extracted on retreat panel completion 95 

81. Rooms extracted on advance and retreat panel initiation . 97 

82. Rooms extracted on advance and retreat 

pillar extraction sequence 98 

83. Rooms extracted on advance and retreat 

first pillar on advance 99 



PAGE 

84. Rooms extracted on advance and retreat 

second pillar on advance 100 

85. Rooms extracted on advance and retreat 

pillar extraction sequence 101 

86. Rooms extracted on advance and retreat 

first pillar on retreat 102 

87. Rooms extracted on advance and retreat 

second pillar on retreat 103 

88. Rooms extracted on advance and retreat 

third pillar on retreat 104 

89. Rooms extracted on advance and retreat 

fourth pillar on retreat 105 

90. Rooms extracted on advance and retreat 

fifth pillar on retreat 106 

91. Rooms extracted on advance and retreat 

sixth pillar on retreat 107 

92. Rooms extracted on advance and retreat 

seventh pillar on retreat 108 

93. Rooms extracted on advance and retreat 109 

94. Mine strata with intruding structures 114 

95. Distribution of overburden weight 116 

96. Two-dimensional model of subsidence 117 

97. Example of subsidence from underground mining 118 

98. Critical width versus overburden (empirical) 122 

99. Approximate distribution of roof stresses 

above an opening 122 

100. The Voussoir arch principle 123 

101. Pillar strength versus height-to-width ratio 124 

102. Optimum fender width 127 

103. Panel bleeding 129 

104. Panel interconnection 130 

105. Panel connection to bleeders 131 

106. Pillar locations susceptible to bumping during mining . . 133 

107. Split-and-f ender extraction plan for 

supply forecasting 145 



VI 



TABLES 

PAGE 

1. Advantages and disadvantages of panel mining methods. . . 17 

2. Summary of mining practices 24 

3. Ranking of workers by age groups, 1966-75 119 



vxi 



ROOM AND PILLAR RETREAT MINING 

A Manual for the Coal Industry 

by 
Peter W. Kauffman 1 . Steven A. Hawkins 2 , and Robert R. Thompson 3 



ABSTRACT 

This Bureau of Mines publication is designed primarily to provide mine 
engineers and production-level mine managers with the following: 

1. Information to assist them in making the decision to retreat mine and 
in selecting the best retreat mining technique for specific mining 
conditions. 

2. Information on mine planning that will enable them to design mine 
layouts for safe and efficient retreat mining. 

3. Information that will enable them to develop a section foreman's 
handbook. 

The manual has been organized to gradually increase in level of detail as 
the reader progresses from beginning to end. Individuals interested in an 
overview of retreat mining can confine themselves to the first few chapters. 
Those interested in mine planning should read the middle chapters as well. 
Those interested in the development of a foreman's handbook should read the 
entire manual. 

Chapter 1. INTRODUCTION 

Room-and-pillar retreat mining, because of its complexities, can be 
effectively practiced only if mine management carefully develops a plan for 
mining and communicates this plan to the section foreman. This publication 
is designed to provide information to mine managers that will enable them to 
analyze all options and select and develop a mining plan that meets their 
particular needs. However, once the appropriate plan has been selected, the 
information must be effectively communicated to the section foreman. The 
most effective manner of accomplishing this is a simplified handbook that 
details the routine operations so that the foreman knows exactly the roof 
support, ventilation, and haulage requirements for any given cut. 

The need to plan mine operations at this level and to communicate these 
detailed plans to mine foremen can be seen by looking at the mining industry 

1/ Principal, Management Engineers Incorporated, Reston, Va. 
2/ Senior Associate, Management Engineers Incorporated, Reston, Va. 
3/ Research Structural Engineer, Spokane Research Center, Bureau of Mines, 
Spokane, Wash. 



today. Those mining companies with a reputation for efficient and safe oper- 
ations are planning at this level, and those with poorer operations generally 
are not. This manual will be of assistance to those mining companies inter- 
ested in developing such a communication process, but each mining company 
must commit the resources to develop the handbook and follow up on its imple- 
mentation and refinement. 

The use of this manual depends to some extent on the user's needs and 
intentions. Mine managers — the primary users — should first be familiar with 
the range of retreat mining practices contained in chapter 2, Summary and 
Comparison of Mining Techniques. After reading this chapter, they will have 
an overview of the terminology and techniques that will be used throughout 
the remainder of the manual. Second, they should review chapter 3 and the 
appendix to find those techniques used by other mines in their area or under 
similar conditions. Third, they should study the detailed descriptions of 
the techniques that they wish to use. 

Mine planners should review not only the same material as mine managers 
but also the information provided in chapters 6 and 7 to ensure that the 
physical conditions in which their operations are conducted are suitable for 
efficient retreat mining and that they comply with the regulations. Those 
individuals responsible for developing a foreman's handbook should review all 
chapters, particularly the information provided in chapters 8 and 9. Other 
users of this manual may be most interested in information provided in one 
particular chapter. Care should be taken to ensure that material is not 
taken out of context. 

Chapter 2. SUMMARY AND COMPARISON OF MINING TECHNIQUES 

Room-and-pillar retreat mining techniques vary widely over the United 
States. The techniques used in a particular area are dependent upon specific 
local conditions, the influence of experiences of adjacent mines, and the 
experience of local Mine Safety and Health Administration (MSHA) roof control 
specialists. This chapter contains a summary of each process for the extrac- 
tion of individual pillars and each method of mining production panels. The 
material is presented without discussion of the relative success of each 
technique. Chapter 3 contains a discussion of the areas in the country 
employing each technique, and chapters 4 and 5 describe the most successful 
techniques with respect to safety and productivity. 

Pillar Extraction Processes 

In the course of selecting a pillar extraction process, the mine engineer 
should restrict himself, with few exceptions, to the widely used processes 
described in detail in chapter 4. The exceptions are the less common 
processes presented in the latter part of this chapter; these can be 
practiced successfully only in particular conditions and should not be 
attempted unless these conditions prevail. 

Common Pillar Extraction Processes 

Pillar extraction processes widely practiced in the industry include 
split and fender, pocket and wing, outside lifts, and open ending. The 
following discussions are intended to provide a brief summary of applicable 
processes; accordingly, much of the detail commonly found in roof control 



plans is omitted. For the more widely used techinques, all necessary detail 
is included in chapter 4. 

Split and Fender 

Split and fender is the most commonly used pillar extraction process in 
the United States. It is best used where a relatively small pillar is to be 
extracted; however , a large pillar can be extracted using multiple splits. 
The basic concept of the process is to mine in a sequence of cuts through the 
pillar, generally parallel to the pillar's long side. This mining forms a 
split through the pillar and creates two fenders of coal. The roof within 
the split may be supported by bolts, posts and timbers, or a combination as 
required. Fenders are extracted from the split or adjacent entry with 
additional support provided by posts. Generally, multiple pillars are 
extracted simultaneously in order to provide an adequate number of working 
places to avoid delays. A typical sequence of cuts is shown in figure 1. 
The numbered areas in the two pillars represent the cut sequence. The 
sequence shown is for continuous mining equipment. Variations are required 
for continuous haulage or conventional mining equipment. 



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FIGURE 1. - Split-and-fender cutting sequence. 



Pocket and Wing 

Pocket and wing is a process used primarily for the extraction of large 
pillars. It is practiced under widely varying conditions throughout the 
country, but only a few mining companies are using it. The pocket-and-wing 
process allows two working places within the same pillar. Pockets are driven 
on the gob sides of the pillar, and lifts are usually sequenced between 
pockets to provide a place for both mining and roof bolting. A wing or 
fender of coal is left between the pocket and the gob. When the pocket is 
completed, the wing is recovered. Additional pockets are driven and wings 
extracted until the pillar is reduced to a final stump or pushout. This 



stump is recovered from the intersection. Additional cuts are sometimes 
required in adjacent pillars to eliminate production delays, h typical 
sequence of cuts is shown in figure 2. 





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FIGURE 2. - Pocket-and-wing cutting sequence. 



Outside Lifts 



The outside-lift pillar extraction process has been used by a few mines 
with very good success. This process is suitable only for small pillars. 
The variations are many, depending upon conditions, pillar dimensions, and 
equipment. Generally, the pillar is dimensioned so that lifts taken from one 
side of the pillar are sufficient to extract the pillar without going beyond 
supported roof. The sequence of cuts involves taking lifts from the pillar 
beginning near the gob and moving toward solid coal. The sequence of cuts 
shown in figure 3 is typical. 

Open Ending 



This process for pillar extraction is used widely by mines using 
conventional mining equipment. The process consists of taking lifts in a 
sequence of cuts generally on one side of a pillar. Cuts are taken from as 
many as six pillars simultaneously, each ^t a different stage of the five 
conventional operations of cut, drill, shoot, load, and bolt. The pillar 
line is generally at a 4 5-degree angle. The sequence of cuts shown in figure 
4 is for one pillar only; however, similar cuts are made simultaneously in 
the other pillars in the line. 



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FIGURE 3. - Outside-lift cutting sequence. 



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FIGURE 4. - Open-ending cutting sequence. 



Variations of Basic Processes 

Split-and-Fender Modifications 

Because split and fender is the most commonly practiced pillar extraction 
process in the United States, it is also the most widely modified. Six of 
the variations are sufficiently adaptable to make them worthy of mention in 
this chapter. 

Multiple Splits . The single split process shown in figure 1 is suitable 
for the mining of many of the smaller pillars used in the United States. If 
pillar width exceeds 4 5 feet, however, it is no longer possible to extract 
the fenders remaining after a single- split is taken through the pillar. To 
accomplish the extraction of these larger pillars, many mines take two or 
three splits through the pillars. A typical cut sequence for removal of 
pillars using two splits is shown in figure 5. 



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22 

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17 

18. 
19 


6 


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FIGURE 5. - Multiple splits. 

The pillars shown are approximately 65 feet wide. Notice that cuts in 
the second split in the inby pillar are sequenced with the first split in the 
outby pillar: that is, cuts 21 and 22 are identical to cuts 1 and 2, respec- 
tively. Similar plans can be developed for three splits. It should be 
pointed out that when extracting large pillars, the use of the pocket-and- 
wing extraction process may be preferable to the use of a multiple-split-and- 
fender process. 

Christmas Treeing . This practice involves taking two fenders from the 
same split or entry. Two sequences are prevalent. The first involves the 
extraction of a single pillar. As shown in figure 6, cuts are made to the 
left and then to the right (8 before 9, 10 before 11, etc.). 



The second method, shown in figure 7, involves the extraction of two 
pillars from the same entry. In this sequence, extraction of the final stump 
is difficult; often this stump must be sacrificed. 

In both Christmas treeing methods, the continuous miner is beneath the 
middle of a relatively large unsupported span rather than near a rib pro- 
tected by solid coal. Exposure is greatly increased. These methods are most 
often used when access to the pillar through an entry or crosscut has been 
blocked or when leaving a partial pillar would create a dangerous hanging 
fall. Use of either of these methods is not encouraged under normal circum- 
stances. 

Indicator Stump . Another variation of the split-and-f ender process is 
the indicator stump. The final cuts in the split are angled outward in a 
manner that leaves a wedge-shaped stump in the center of the end of the 
split, as shown in figure 8. The crew observes the rate of disintegration of 
the stump as an indicator of roof activity while the inby fender is being 
extracted. 

Fender Breakthrough . One variation that can be used with either of the 
pillaring processes involving fenders (split-and-fender and pocket-and-wing) 
is the fender-breakthrough technique. This technique is generally used in 
locations where narrow fenders (approximately 8 feet) are used and involves 
periodically breaking through the inby fender into the gob as the split is 
being advanced. These breaks serve as indicators of the fender thickness to 
aid the miner operator and also aid in ventilation. A typical cut sequence 
showing these breaks in shown in figure 9. After the split is completed, the 
fender is extracted in the normal fashion. 

Fender Notching . This technique involves cutting a notch to the left of 
the split as the fender to the right is extracted. This practice can be used 
to increase recovery with minimal exposure to hazardous conditions. A typi- 
cal cut sequence (fig. 10) involves the removal of small wedge-shaped cuts of 
coal from the outby fender as the inby fender is being removed. Ideally, the 
positioning of these notch cuts coincides with the lifts that will be removed 
from the outby fender when that fender is recovered from the entry or split. 
Since these cuts are taken from under supported area, no hazardous exposure 
is created. 

Conventional Split and Fender . The split-and-fender process is also used 
with conventional mining equipment. The use of conventional mining equipment 
may be desirable when mining a hard coal or coal layered with rock. However, 
these conditions require large charges to break the coal. With open ending, 
such a charge might result in a high percentage of the coal being blown into 
the mined out area. The use of the split-and-fender technique confines the 
coal between the fenders and increases the recovery rate. A typical 
extraction sequence is shown in figure 11. 



mm 



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FIGURE 6. - Christmas-treeing cutting sequence (one pillar) 



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FIGURE 7. - Christmas-treeing cutting sequence (two pillars) 



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FIGURE '10. - Fender-notching cutting sequence. 



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FIGURE 11. - Split-and-fender cutting sequence 
using conventional mining equipment. 



10 



Pocket-and-Wing Variations 

Three of the variations to split-and-f ender pillar extraction can also be 
used in the extraction of pillars by the pocket-and-wing process — Indicator 
stump, fender breakthrough, and fender notching. One other pocket-and-wing 
variation used quite commonly is nonsequential pocket and wing. This varia- 
tion is made possible by the use of miners with on-board bolters or the use 
of boring-type continuous miners. In areas of high gas and frail top, the 
nonsequential pocket-and-wing technique can prove very beneficial, since air 
can be directed to a single face throughout the extraction process. A typi- 
cal cut sequence for this variation is shown in figure 12. It should be 
noted that with the pocket-and-wing method, any number of pockets can be 
driven, as required by the physical dimensions of the pillar block and as 
restricted by law. 

Outside-Lift Variations 

The basic outside-lift cut sequence that was shown in figure 3 is very 
limited in its application. Because of the practical limitations on miner 
reach, the technique cannot be used with pillars significantly wider than 20 
feet. This process is generally applicable for the removal of room pillars, 
with the use of other techniques to remove the chain pillars. 





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FIGURE 12. - Nonsequential-pocket-and-wing cutting sequence. 

A variation of the outside-lift process that closely resembles the 
practice of split-and-f ender Christmas treeing is a combination of outside 
lifts and Christmas treeing. Using this process, it is possible to extract 



11 



pillars up to 30 to 3 5 feet wide, but even these pillar dimensions limit the 
use of the process to areas of low overburden pressures and easily breakable 
top. This process results in significantly greater amounts of extracted coal 
without bolting (free coal) than any other pillar extraction process 
presented. However, the increase in free coal must be carefully weighed 
against the hazards involved with use of this modification. A typical 
sequence of cuts for outside-lift Christmas treeing is shown in figure 13. 





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FIGURE 13. - Cutting sequence for outside-lift Christmas treeing. 

Other Pillar Extraction Processes 

Although the vast majority of pillar extraction processes in use in the 
United States fall into one of the four basic process classifications, there 
are a number of other extraction processes in use. Because these processes 
are not acceptable under all conditions, are subject to many equipment 
limitations, and are not recommended for mines not experienced in pillar 
extraction, they are not included in this report. 

Methods of Mining Production Panels 

The primary methods of mining production panels are described in this 
section. The group of entries driven into the panel is referred to as a 
panel entry set. Each panel entry set may include three to eight or more 
entries. The pillars formed by the panel entry set are referred to as chain 
pillars. Any rooms driven off the panel entry set are referred to as 
production rooms, and the resultant pillars are called production pillars. 

The basic methods used by the industry include the following: 

1. Full panel extracted on retreat. The full panel is developed with no 
differentiation between the panel entry set and production rooms. The 
entire panel is extracted on retreat. 

2. Rooms driven and extracted on retreat. The panel entry set is 
developed with production rooms driven and pillars extracted on 
retreat. 



12 



3. Rooms driven and extracted on both advance and retreat. The panel 
entry set is developed with production rooms driven and production 
pillars extracted on one side while advancing the panel and on the 
other side while retreating the panel. 

4. Rooms only. The panel entry set is developed with rooms driven while 
advancing and retreating the panel with no recovery of pillars. 

In all designs, a panel entry set forming the neck is started off the 
submains for a distance sufficient to provide an adequate barrier pillar. 
The panel is then normally widened. The width of the panel usually ranges 
from 300 to 600 feet and is dictated by haulage constraints or other 
factors. The length of the panel is usually 2,000 to 4,000 feet depending on 
the length of panel belt, the use of rail, or other factors. 

Full Panel Extracted on Retreat 



In this design, a full width panel consisting of as many as 10 to 12 
entries is developed off the neck. The panel is developed to the designated 
length. After development, a bleeder system is established and pillar 
extraction is begun. A pillar line is established either at an angle, common 
to both continuous and conventional mining, or flat (90O) , common to 
continuous mining. Pillars are extracted until the entire panel has been 
mined. Figure 14 shows a typical configuration for full panel extracted on 
retreat. 






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FIGURE 14. - Full panel extracted on retreat. 



13 



Rooms Driven and Extracted on Retreat 

In this design, a panel entry set usually only large enough to handle the 
necessary ventilation, haulage, and other supporting functions (generally 
three to five entries) is completely developed to the designated panel 
length, and the panel entry set is connected to the bleeder system. During 
retreat from the panel, rooms are driven and pillars extracted on the way out 
of the rooms. The rooms may be developed and extracted on only one side or 
in groups alternately on both sides of the entry set. Pillar lines can be 
flat or angled. This method is not practiced using conventional mining 
equipment because of limitations on the number of working places. Figure 15 
shows a system where rooms are driven off only one side of the panel and the 
production and chain pillars are extracted. 



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FIGURE 15. - Rooms driven and extracted on retreat. 

Rooms Driven and Extracted on Advance and on Retreat 

In this design, as the panel is developed, rooms are driven, and pro- 
duction pillars are extracted on one side of the panel entry set. When the 
panel entry set is completed, a bleeder is established. Rooms are then 
driven and the pillars extracted on the other side of the panel entry set as 
the panel entry set is retreated. The pillar line can be flat or angled. 



14 



Due to limitations on the number of working places, this method is not prac- 
ticed with conventional mining equipment. Figure 16 shows this configura- 
tion. 



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FIGURE 16. - Rooms driven and extracted on advance and on retreat. 

Rooms Only 

In this method, a panel entry set only large enough to handle the neces- 
sary ventilation, haulage, and other supporting functions is developed to the 
designated panel length. The entry set is connected to the bleeder system. 
Production rooms in sets of four or five are driven in both directions as the 
equipment is retreated from the panel. No second mining is conducted. This 
system can be employed with any equipment. Figure 17 shows a typical config- 
uration. 

Evaluation of Methods 

Each of the four retreat mining methods presented have certain advantages 
and disadvantages. Each is used successfully in one area or another of the 
United States. Table 1 lists the specific advantages and disadvantages of 
each method, keyed to the following desirable features. 

1. Active places should not be maintained near a caved area. The increased 
pressures in the vicinity of a caved area make these areas less desirable 
for active workings. 



15 



2. The length of time that openings are maintained should be minimal. 
Reducing the amount of time that the roof is exposed to air and moisture 
will decrease the rate of deterioration. 

3. Solid coal should be retained on one side of the panel entry set to 
reduce pressures on the chain pillars. 

4. Workplaces should be concentrated in a limited area. This decreases the 
area of control for the section foreman and allows for more effective 
management of the operations. 

5. Tonnage produced between major logistic changes such as belt moves, track 
moves, or power center moves should be as high as possible. This reduces 
the percentage of nonproductive time. 

6. Average haul distances should be minimized to increase efficiency and 
help reduce nonproductive time caused by haulage delays. 

7. The ventilation system should operate with a minimum number of changes 
from one cut to another. This reduces nonproductive time and required 
supervision. 

8. The bleeder system should be easy to establish and maintain to help 
reduce ventilation problems. 

9. The maximum amount of reserves should be recovered. Coal left in the 
panel is lost and decreases the economics of the operation, assuming a 
cost-effective recovery rate. 









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FIGURE 17. - Rooms only. 



16 



TABLE 1. - Advantages and disadvantages of panel mining methods. 



Retreat Mining Method 



Advantages 



Disadvantages 



1. Full panel extracted on retreat 




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1- No active place need be main- 
tained near a caved area. 

3. Solid coal on one side of the 
panel. 

"5. Highest tons extracted per 
belt move. 

6. Short average haulage distance. 

7. Easily ventilated. 

8. Easily bled. 

9. Maximum recovery of reserves. 



Roof must be maintained 
for a long period over 
the life of the panel. 

Work places are not 

concentrated. 



Room driven and extracted on retreat 




1. No active place need be main- 
tained near a caved area. 

2. Short time to maintain roof. 

3. Solid coal on one side of the 
panel. 

4. Work places are concentrated. 

7. Easy to ventilate. 

8. Easily bled. 

9. Maximum recovery of reserves. 



5. Low tons extracted per 
belt move. 



Fairly long average haul 
distance . 



Room driven and extracted on 
advance and on retreat 




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2. Short time to maintain roof. 
4. Work places are concentrated. 
9. Maximum recovery of reserves. 



1. Active place must be main- 
tained near a caved area. 

3. Solid coal not on one side 
of panel entry set. 

5. Low tonnage extracted per 
belt move. 

6 . Fairly long average haul 
distance. 

7. Difficult to ventilate. 

8. Difficult to bleed. 



4 . Room only 




1. No active place need be main- 
tained near caved area. 

2. Short time to maintain roof. 

3. Solid coal on one side of the 
panel. 

4. Work places are concentrated. 

7. Easy to ventilate. 

8. Easily bled. 



5. Low tonnage extracted per 
belt move. 

6. Fairly long average haul 
distance. 

9. Poor recovery of reserves. 



17 



Chapter 3. REGIONAL RETREAT MINING PRACTICES 

This chapter contains a discussion of the retreat mining practices in 
each geographic region in the country. The geographic regions are divided 
according to the MSHA Districts. The mining practices and, specifically, the 
pro esses utilized to extract pillars are presented. There are 10 MSHA 
Health and Safety Districts in the United States (fig. 18) . The retreat 
mining practices in all but one of the districts are discussed in the 
material that follows. MSHA District 1 is not discussed since this district 
contains only anthracite coal mines. A more detailed breakdown of retreat 
mining practices by seam is contained in the appendix. 

MSHA District 2 

District 2 encompasses the bituminous coal fields of western Pennsyl- 
vania. Coal is found primarily in six seams: Upper Freeport, Pittsburgh, 
Lower Kittanning, Lower Freeport, Upper Kittanning, and Sewickley. Mining 
also takes place in the Clarion, Middle Kittanning, and Brookville seams. 

Some of the important features and techniques in District 2 are as 
follows: 

1. The split-and-f ender process dominates the mines in the eastern 
portion of the district (the Freeport and Kittanning seams) . Success 
is being achieved with the outside-lift process in some of the mines 
in the Freeport seams. The seams in this area of the district tend to 
be in more heavily folded strata and under lower overburden pressures 
than seams at the western end of the district. 

2. In the Pittsburgh seam in the western end of the district, the 
pocket-and-wing process is most common. The Pittsburgh seam is the 
most important seam in the district volumetrically and is one of the 
major producing seams in the United States. This area, and its 
corresponding area in District 3, are the main users of the 
pocket-and-wing process in the United States. 

3. Overall, 85 out of 122 (70 percent) of the mines in the district have 
some form of a pillar extraction plan on file. 



18 



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19 



MSHA District 3 

District 3 comprises the northern portion of West Virginia (including the 
panhandle) and the western counties of Maryland. It shares many mining char- 
acteristics with the western portion of District 2, which lies immediately to 
the north. Mining takes place in a total of 12 seams in the district. Sig- 
nificant mining takes place in seven of these seams: Pittsburgh, Upper Free- 
port, Sewell, Redstone, Sewickley, Middle Kittanning, and Peerless. 

Some of the notable features of District 3 are as follows: 

1. In the Pittsburgh seam, pillar extraction is difficult in the areas of 
the district near the Ohio River (Marshall and Brook Counties) because 
of a massive limestone main roof. In Monongalia and Marion Counties, 
the conditions are similar to the western portion of District 2, and 
the pocket-and-wing pillar extraction technique prevails. 

2. Full pillar extraction is not common in the Upper Freeport seam in the 
district. A limited number of mines are having success with full 
pillar extraction of the Upper Freeport seam in Grant County using the 
outside-lift process. 

3. Full pillar extraction is practiced successfully in the Redstone seam 
using the split-and-fender process. 

4. Districtwide, 79 of 132 (60 percent) of the roof control plans include 
pillar extraction plans. 

MSHA District 4 

District 4 is the largest district (in terms of number of mines) under 
the control of MSHA. District 4 comprises the southern counties of West 
Virginia. Mining takes place in 35 seams in District 4, 29 of which contain 
5 or more mines. Some of the notable features of District 4 pillar 
extraction processes are as follows: 

1. Of the most active 15 seams in the district, only the Pocahontas seam 
has a majority of mines practicing pillar extraction. 

2. All seams have a significant number of mines practicing pillar 
extraction successfully. This implies that, in general, there is no 
geologic limitation to discourage mining companies in this area from 
practicing pillar extraction of some form. 



20 



3. In total, only 371 of 1,069 roof control plans (35 percent) showed 
some form of pillar extraction. 

MSHA District 5 

District 5 comprises the Commonwealth of Virginia. Mining takes place in 
18 seams in 5 western counties in Virginia. Fifteen of these seams contain 
five or more coal mines. Some notable features of District 5 pillar 
extraction practices are as follows: 

1. Roof control plans for the majority of mines in any seam in the 
district do not indicate pillar extraction. 

2. Only 198 of 965 roof control plans (21 percent) show some form of 
pillar extraction. A significant number of mines do practice pillar 
extraction, however, in most seams in Buchanan County. 

MSHA District 6 

District 6 comprises the northeastern section of Kentucky. Mining is 
conducted in 16 seams, 13 of which contain 5 or more mines. Some of the 
notable features of District 6 pillar extraction practices are as follows: 

1. Roof control plans for the majority of mines in any seam do not 
indicate the use of any secondary pillar extraction techniques. 

2. Only 181 of 888 roof control plans (20 percent) show some pillar 
extraction. The vast majority of these are partial extraction. Full 
pillar extraction is practiced almost solely in Pike and Letcher 
Counties. 

MSHA District 7 

District 7 encompasses large portions of the Southeastern United States. 
The significant coal mining areas are located in the States of Alabama, 
Tennessee and Kentucky. Each State's retreat mining practices will be 
briefly mentioned. 

Alabama 

Mining is conducted in six seams in Alabama. Three of these seams have 
five or more mines. Only 9 of 28 roof control plans show pillar extrac- 
tion processes. Only in the Pratt seam is pillar extraction shown in the 
majority of roof control plans. Open-end pillar extraction is relatively 
common among those mines practicing pillar extraction in this area. 



21 



Kentucky 

Mining is conducted in 16 seams in the central portion of Kentucky 
included in District 7. Nine of these seams contain five or more mines. 
Pillar extraction does not predominate in any seam in this district. Only 86 
out of 586 roof control plans (15 percent) show the use of any pillar 
extraction processes. The number and location of mines practicing at least 
partial pillar extraction, however, indicate that pillar extraction in this 
district is possible in most seams. 

Tennessee 

Mining is conducted in 20 seams in the eastern portion of Tennessee. Ten 
of these seams contain five or more mines. Only 21 of 220 roof control plans 
(10 percent) show pillar extraction processes. Pillar extraction does not 
predominate in any seam in the district. There are partial pillar extraction 
plans on file for mines in the Dean and Sewanee seams, indicating that pillar 
extraction in these seams is possible. 

MSHA District 8 

District 8 comprises the majority of the Illinois Basin coalfield. 
Mining in District 8 takes place in Illinois, Indiana, and Ohio. Ohio's coal 
mining areas are in the Appalachian region and will be discussed separately 
from Illinois and Indiana. 

Illinois and Indiana 

Mining takes place in four seams in Illinois and Indiana. Fourteen of 31 
roof control plans (45 percent) for the area contain some form of pillar 
extraction. 

The major seam in the district is the Illinois No. 6 or Herrin seam. 
Extensive retreat mining takes place in the seam in Franklin and Jefferson 
Counties. 

Ohio 

The eastern portion of Ohio contains minable seams that are on the 
western edge of the Appalachian coalfield. No full pillar extraction takes 
place in this area due to massive limestone in the main roof and problems 
associated with pressure overrides. Fourteen of 29 roof control plans (48 
percent) for the area do contain plans for partial pillaring. The greatest 
concentrations of pillaring are in the Pittsburgh Nos. 8 and 6A (Lower 
Freeport) seams. All mines in the Pittsburgh No. 8 seam and all but one in 
the No. 6A seam practice partial pillar extraction. 



22 



MSHA District 9 

District 9 includes most of the coal mining States west of the Missis- 
sippi River. Iowa, Missouri, Arkansas, Louisiana, Kansas, Oklahoma, and 
Texas are included in District 10, since they have recently been transferred 
from this district. Underground coal mining takes place in four of the 
remaining States: New Mexico, Wyoming, Colorado, and Utah. 

One underground mine is located in Wyoming. It does not practice pillar 
extraction. Both of the underground mines in New Mexico practice pillar 
extraction using the split-and-fender process. 

In Colorado, underground mining takes place in 18 coal seams. Only two 
seams contain five or more mines. Fourteen of the 32 roof control plans for 
the State (44 percent) contain plans for some form of pillar extraction. 

Underground coal mining in Utah takes place in 11 seams. Only the 
Hiawatha seam contains five or more mines. Nineteen of the 27 roof control 
plans for Utah (70 percent) contain pillar extraction plans. Split-and- 
fender extraction is shown in 17 of these plans. 

MSHA District 10 

District 10 is comprised of western Kentucky, western Tennessee, and — 
since the recent transfer of seven States from District 9 to District 10 — 
Iowa, Missouri, Arkansas, Louisiana, Kansas, Oklahoma, and Texas. Arkansas, 
Iowa, and Oklahoma have a total of six underground mines, none of which 
practices pillar extraction. 

There are 28 underground mines in western Kentucky. One mine is con- 
ducting partial pillaring using outside lifts on a trial basis. The mining 
operations are generally under little overburden in flat farming areas, and 
subsidence is felt to be undesirable because it would affect the water table 
upon which the farming depends. 

Summary 

Table 2 summarizes the retreat mining practices for each district. 
Further, the appendix includes charts that summarize the mining practices 
classified by MSHA district, State, seam, and county. Each table indicates 
county, number of roof control plans, the most popular process, the number of 
mines using each of the full extraction methods, the number of mines using 
partial extraction methods, and the number of mines that do not pillar. 



23 



TABLE 2. - Summary of mining practices 







| 
Number of 


Number of 


Percentage 






roof control 


with pillar 


of mines with 


District 


Area 


plans reviewed j 

i 


extraction plans 


extraction plans 


2 


Western Penn- 










sylvania 


122 


85 


70 


3 


Northern West 
Virginia and 










Maryland 


132 


79 


60 


4 


Southern West 










Virginia 


1,069 


371 


35 


5 


Virginia 


965 


198 


21 


6 


Northeastern 










Kentucky 


888 


181 


20 


7 


Alabama 


28 


9 


32 




Central Kentucky 


586 


86 


15 




Eastern Tennessee 


220 


21 


10 


8 


Illinois and 










Indiana 


31 


14 


45 




Ohio 


29 


14 


48 


9 


Colorado 


32 


14 


44 




Wyoming 


1 










Utah * 


27 


19 


70 




New Mexico 


2 


2 


100 


10 


Western Ken- 
tucky and 
western Ten- 










nessee 


28 










Iowa, Missis- 










sippi, Alaska, 










Lousiana, Okla- 










homa, Kansas, 










and Texas 


6 








All 


United States 


4,166 


1,093 


26 



24 



Chapter 4. THE BASIC PILLAR EXTRACTION PROCESSES 

Chapter 2 presented a summary description of common panel extraction 
methods and pillar extraction processes. The four basic pillar extraction 
processes are described in detail in this chapter. These processes — split 
and fender, pocket and wing, outside lift, and open ending — with their 
variations, account for nearly all production from full retreat mining and 
are adaptable for use under almost any set of background conditions in which 
it is possible to retreat mine. In the present chapter, information that 
will aid in choosing the best process to use is presented, including the 
characteristics, limitations, and geographical areas of successful usage. 

The drawings in this chapter, which are reprinted from a contract report, 
reflect the appearance of the workplace immediately following the completion 
of mining. The positions of curtains and timbering are as they would appear 
at the completion of the cut. Where more than one cut is shown, the posi- 
tions for timbers, ventilation, and haulage are for the first cut only. 

Split and Fender 

The split-and-f ender process, also known as the split-and-wing or split- 
and-pillar process, is the most commonly used pillar extraction process in 
the United States. The characteristics of the process and the conditions 
under which it is frequently used are described below, as well as the areas 
of the country and seams in which the split-and-fender process is practiced. 

Description of the Process 

The basic concept of the split-and-fender process is to mine through an 
existing pillar generally parallel to the pillar's long side. This process 
forms a split through the pillar and creates two fenders of standing coal, 
one on either side of the split. The roof within the split is supported. 
The width of these fenders is, ideally, such that they can be wholly 
extracted within the mining equipment's reach without requiring additional 
roof support. This limitation usually dictates a maximum pillar width of 40 
to 45 feet. If this is not the case, it may be necessary to extract the 
pillar by taking multiple splits or using a pillar extraction process better 
suited to large pillars (such as pocket and wing) . 

The split-and-fender process generally involves mining simultaneously at 
least two pillars. If roof support activities can be accomplished simul- 
taneously with mining (using onboard bolting or some similar means) , or if 
extensive delays for roof support can be tolerated, then split and fender can 
be practiced within a single pillar. When an odd number of pillars are on a 
pillar line or when the amount of time to install roof support in a split is 
longer than the amount of time to mine the split, it may be advantageous to 
mine three pillars simultaneously. The split-and-fender process will be 
detailed in the material that follows. Figures 19 through 32, which illus- 
trate the process, depict two pillars with sequential mining. 



25 



The overall cut sequence for split - and - fender pillar 
recovery is shown. 

ROOF SUPPORT: Breaker posts have been placed at all 
openings to the gob. Roadways have been 
narrowed to 16 feet. 



VENTILATION: 
HAULAGE: 



Shown on individual cut illustrations. 

Locations of change-out. points and haulage 
limitations will be discussed on the 
individual cut illustrations. Haulage 
paths are shown on the panel extraction 
plans detailed in Chapter 5. 



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23 



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LEGEND 



— » Intake Air 
■— •• Return Air 
— y Face Curtain 
■€— Check Curtain 
■F- Fly Curtain 
= Stepping 
:f>\ZZ Regulator 



(A) Cable Anchor Point 
-— - Shuttle Car Path 

V7 Discharge Point 

Roadway /Turn Poata 

t : X Breaker Poata 

# Cribbing 
Cob 



Split-and-Fender 
Overall Cut Sequence 



HO282021 



Figure 19 



26 



The first cut in the split-and-f ender process is shown in 
this figure. This cut will be made in the pillar closest 
to the gob. In order to avoid pillar pressure points, it 
is important to extract pi^Mars from the gob side of the 
solid side of the panel. 



ROOF SUPPORT: 



Turn posts are set across the crosscut 
leading into the split before Cut 1 is 
initiated. 



VENTILATION: 



HAULAGE : 



Placement of the face curtain is such that 
intake air sweeps the face of the split 
and returns through the gob. 

The placement of roof support and 
ventilation allows the change-out at the 
first intersection outby the working 
place. The position of the tailpiece on 
the miner may necessitate use of the next 
intersection outby during the early 
portions of this cut. 




— » Intake Air 

> • Return Air 

— y Face Curtain 

-€~~ Cheek Curtain 

-F- Fly Curtain 

=T Stopping 

ZR— Regulator 



LEGEND 



(A) Cable Anchor Point 
— Shuttle Car Path 

V Discharge Point 
• • • • Roadway /Turn Posts 
". 1 1 ". Breaker Posts 

# Cribbing 
Cob 



Split and Fender 
Cut 1 



HO282021 I Figure 20 



27 



The 

patt 

circ 

gob 

cond 

as i 

imme 

used 

inte 

be 

not 

oper 



ventilation shown in Figure 
ern; however, it will 
umstances. In particular, tha 

that will draw a significant 
itions in the mine dictate tha 
s true of many mines with frai 
diate roof, the pattern shown 

This change basically invo 
rsection inby the first split 
drawn ' back through the inby e 
be repeated but should serve 
ating under these conditions. 



24 is the preferred 
not work under some 
t pattern is based on a 

volume of air. If the 
t this is not the case, 
1, unconsolidated shale 
here will have to be 
Ives posting off the 

to allow return air to 
ntry. This figure will 
as an example for mines 




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' '' : 'W 



]:\::f 



LEGEND _ 

► Intake Air (a) Cable Anchor Point 

•— • Return Air — -- Shuttle Car Path 
— * Ftn Curtain V Discharge Point 

"€"- Cheek Curtain •••■ Roadway /Turn Posts 

•F- Fly Curtain \..\ B realtor Posts 
= Stopping ^ Cribbing 

iR— Regulator %&&* Co ° 



Split and Fender 
Cut 1 - Alternate Ventilation 



HO282021 | Figure 21 



28 



Cuts 2, 4, and 


6 form the split in the outby pillar. 


ROOF SUPPORT: 


Turn posts are set in the crosscut leading 




into the split. The breaker posts across 




the crosscut are not required for roof 




support but may be set to eliminate two 




trips by the timber crew. Roof bolting 




takes place in cuts 1, 3, and 5 while cuts 




2, 4, and 6 are being mined. j 


VENTILATION: 


The only way to ventilate split and fender 




pillar extraction and avoid having workmen 




in dust is to use some form of 




double-split ventilation such as that 




shown. The return air from this pillar 




will vent into the panel return while the ! 




return air from the first pillar vents 




into the gob. Complete panel ventilation 




patterns for this technique are shown in 




detail in the next chapter. 


HAULAGE: 


The change-out is in the second crosscut 




outby. 


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L. i 


LEGEND 
* Intake Air (X) Cable Anchor Point 




>— * Return Air 
— ' Face Curtain 


— Shuttle Car Path 
^7 Discharge Point 


Split and Fender 


-€"" Check Curtain 


• • • • Roadway /Turn Post* 


Cuts 2, 4 and 6 


-F- Fly Curtain 


'. Breaker Posts 




ZSSH Stopping 


# Cribbing 




ZH— Regulator 






■ 


< 


Sob 






HO282021 [ Figure 22 



29 



Cuts 3, 5, and 7 complete the split in the inby pillar. 

'ROOF SUPPORT: Cuts 3 and 5 are bolted after they are 

completed (during the mining of Cuts 4 and 
6 respectively) . Breaker posts will be 
placed across the end of the split after 
Cut 7 is completed. 



VENTILATION: 



Same as Cut 1. The brattice curtain is 
advanced to stay within. 10 feet of the 

face. 



HAULAGE : 



The change-out is in the second crosscut 
outby. 







...... m i •;'■••£■ ' V • ■; ■ • t 1 1 i 1 1 1 1 1 i l iiii i'i 1 1 • • 11 '• • 1 1 • I lili-v v- •■•■;•••• t ■' t ■ .v. iiViViViVri ni ■■■:■• 










LEGEND 



— * Intake Air 

—• Return Air 

—. s Face Curtain 

■&- Check Curtain 

•F- Fly Curtain 

Z^Z Stopping 

:ft— Regulator 



Cable Anchor Point 
Shuttle Car Path 

V Discharge Point 
• ■ • Roadway /Turn Post* 
:*.:: Breaker Posts 

# Cribbing 
Gob 



Split and Fender 
Cuts 3, 5, & 7 



HO282021 I Figure 2 3 



30 



Cut 8 is the first lift into the inby fender created by 
the completion of the split through the pillar. 



ROOF SUPPORT: 



Breaker posts have now been set across the 

end of the split. A row of turn posts is 

set across the split leading into the 
active lift. 



VENTILATION: 



The air will split and be directed through 
the split across the faces and into the 
gob. It may be necessary to place a 
curtain on the turn posts leading into the 
cut in order to direct air across the cut. 



HAULAGE : 



Shuttle car paths and change-out points 
will be identical to those used previously 
for Cuts 3, 5, and 7. 
















-^ 














LEGEND 



— » Intake Air 

""• Return Air 

— <" Face Curtain 

"€— Check Curtain 

•F- Fly Curtain 

^S Stopping 

I A— Regulator 



(A) Cable Anchor Point 
Shuttle Car Path 

TJ Discharge Point 
• — Roadway /Turn Poati 
'.'.'.'. Breaker Poata 

# Cribbing 
Cob 



Split and Fender 
Cut 8 



HO282021 | Figure 24 



31 



Cuts 9 through 11 complete the extraction of the first 
fender . 



ROOF SUPPORT 



Prior to the initiation of each cut, a row 
of turn posts is placed across the split 
leading into the cut. The turn posts for 
Cut 9 are shown below. 



VENTILATION: 
HAULAGE: 



Identical to Cut 8. 
Identical to Cut 8. 







LEGENO 



— » Intake Air 

— • Return Air 

— S Face Curtain 

■€— Check Curtain 

■F- Fly Curtain 

!^— Stopping 

:fV= Regulator 



Cable Anchor Point 
--- Shuttle Car Path 

^ Discharge Point 
• — Roadway /Turn Posts 
'.'.'.'. Breaker Posts 

# Cribbing 
Gob 



Split and Fender 
Cuts 9-11 



HO282021 J Figure 25 



32 



Cuts 12, 13, 
first pillar: , 

ROOF SUPPORT 



and 14 are made in the outby fender of the 



Breaker posts are set across the crosscut 
leading into the area where mining was 
just completed. A row of turn posts is 
set across the entry leading into each 
cut. The turn posts for Cut 12 are shown 
below. 



VENTILATION: 



HAULAGE 



The check curtain placed across the cross- 
cut forces air through the entry. It may 
be necessary to place a curtain across the 
entry to direct air into the cuts. 

The change-out is in the second crosscut 
outby. 






iiiifctMJiiiitm* 







13^ 















:•:+:•:•:•:•:•:•:+:•:•:*•:•:•:«•:•:•:«>: 



:'. 






LEGEND 



Intake Air 
Return Air 
S Face Curtain 
£— Check Curtain 
F- Fly Curtain 
=T Stepping 
rt= Regulator 



(X) Cable Anchor Point 
Shuttle Car Path 

^7 Discharge Point 
•••• Roadway /Turn Posts 
"I:: Breaker Posta 

# Cribbing 
Cob 



Split and Fender 
Cuts 12-14 



H02 8 



2021 I Figure 26 



33 



Cut 15 is the final cut (pushout) in the extraction of 
the first pillar. 



ROOF SUPPORT 



VENTILATION: 



The installation of extra roof support is 
very important in the mining of the 
pushout. The roadway into the pushout 
must be narrowed to 14 feet using a row of 
breaker posts on each side of the road- 
way. One row of breaker posts will have 
been set after the completion pf Cut 11. 
This was shown in the previous figure. 

Air coming through the entries will flow 
across this cut or through the split of 
the second pillar. 



HAULAGE : 



Identical to Cuts 12-14. 




LEGEND 



— ^ Intake Air 
-?■* Return Air 
— X Face Curtain 
^— Check Curtain 
■F- Fly Curtain 
~ Stopping 
:f\— Regulator 



(X) Cable Anchor Point 

Shuttle Car Path 

V Discharge Point 
•••• Roadway /Turn Poata 

" Breaker Poata 
# Cribbing 
Cob 



Split and Fender 
Cut 15 



HO282021 J Figure 27 



34 



The 16th cut in the split-and -fender sequence 
completion of the split in the second pillar. 



is 



the 



ROOF SUPPORT: 



After the pushout in the previous pillar 
is completed, the roadway will be posted 
with breaker posts and the area previously 
occupied by that pillar will be recognized 
as gob and no longer used as an active 
work area. Breaker posts will also be 
placed across the end of the split once it 
is completed. 



VENTILATION 



HAULAGE 



At the beginning of this cut, some of the 
air will be drawn through the split, 
behind the curtain, and back down the 
return. Once the split is broken through 
to the gob, air will also pass directly 
through into the. gob. Check curtains were 
placed across the entry and crosscut into 
the area just completed. 



The change-out will be at 
crosscut outby the pillar. 



the 



secona 






im iiiy 



. < ...<.4...-.. 4 ...-.- # ... 



16 



MMIMItt 














LEGEND 

— ► Intake Air (a) Cable Anchor Point 

— * Return Air — Shuttle Car Path 

— ■ ' Face Curtain V Discharge Point 

"€— Check Curtain ■ • • • Roadway /Turn Poata 

■F- Fly Curtain '.'.'.' Breaker Poata 

S=T Stopping # Cribbing 

:R= Regulator i|i§ Cob 



Split and Fender 
Cut 16 



HO282021 



Figure 28 



35 



Cuts 17-20 complete the extraction of the inby fender of 
the second pillar. These cuts are performed in an 
identical manner to Cuts 8, 9, 10, and 11 in the first 
pillar . 



ROOF SUPPORT 



The breaker posts placed after the split 
was completed can be seen in this figure. 
A row of turn posts will be placed leading 
into each cut. Turn posts are shown for 
Cut 17 only. 



VENTILATION: 



Ventilation for all of these cuts will be 
directly up the split into the gob. 



HAULAGE : 



The change-out is in the first crosscut 
outby. 




» Intake Air 

1 • Return Air 
S Face Curtain 
-€— Check Curtain 
-F- Fly Curtain 
___ Stepping 
:f\— Regulator 



LEGEND 



(A) Cable Anchor Point 

Shuttle Car Path 

^ Discharge Point 
• • • • Roadway /Turn Posts 

*. Breaker Posts 
# Cribbing 
Cob 



Split and Fender 
Cuts 17-20 



HO282021 || Figure 29 



36 



Cuts 21-23 are the first three cuts in the removal of the 
outby fender of the second pillar in the spli t-and-f ender 
sequence . 



ROOF SUPPORT: 



The row of breaker posts shown near the 
split in this pillar are set after 
completion of Cut 20 in the inby fender. 
A row of turn posts is placed prior to the 
initiation of each cut. The turn posts 
for Cut 21 are shown. 



VENTILATION: 



Ventilation of these three cuts will be 
directly up the entry into the gob. The 
check curtain across the crosscut has been 
moved outby the split. 



HAULAGE: 



The change-out is in the first crosscut. 


















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.22 



i 23 



i ' 






wmm 






- * 
' ' illiiillililllll 



— • Intake Air 
— » Return Air 
_-*" Face Curtain 
"fr- Check Curtain 
•F- Fly Curtain 
~ Stopping 
:f|= Regulator 



LEGEND 



(A) Cable Anchor Point 
Shuttle Car Path 

^ Discharge Point 
• • • • Roadway /Turn Poata 
'.'.'.' Breaker Posts 

# Cribbing 
Cob 



Split and Fender 
Cuts 21-23 



HO282021 



Figure 30 



37 



Cut 24 is the final pushout in the basic, two-pillar 
split-and-fender sequence. 



ROOF SUPPORT: 



Prior to initiating this cut, roadway 
posts must be set to limit the roadway to 
a maximum of 14 feet. The breaker posts 
separating this area from the next pillar 
in the sequence must be set at this time 
as well. After this cut is completed, the 
entrance to the roadway should also have 
breaker posts set across it. These 
actions will effectively isolate the mined 
out area. 



VENTILATION: 



HAULAGE : 



Fresh air will flow directly across 
working place into the gob. 



the 



Because of the roadway limitation, it will 
be possible to access this cut only from 
the entry. The change-out will be in the 
second crosscut outby this area. 






m 






m 

24 § 






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f:S:;:|:i:;S-S|S*:;:;:*:S 



'■■'.■ :■-.:■. 



:■:-:•:•:•:•:-:•:■■.•:•:•:- :-:•:-:*:-:•.*■:•:-;-: ■:• 



''•'>•■•»•'■'■<•■'■;■"• 



r 



Intake Air 
Return Air 
— * Face Curtain 
€~" Check Curtain 
F- Fly Curtain 

«w» Stopping 

ft— Regulator 



LEGEND 



(A) Cabla Anchor Point 
— - Shuttle Car Path 
T7 Discharge Point 
•••• Roadway /Turn Posts 

:: Breaker Poets 
# Cribbing 
Cob 



Split and Fender 
Cut 24 



HO282021 



Figure 31 



38 



If access to the pillar through the entry is not 
possible, the alternative shown here, providing access 
through the crosscut, can be used. 



ROOF SUPPORT 



Breaker posts are placed across the 
entry. The intersection is timbered 
sufficiently to limit access to one 
14-foot roadway. 



VENTILATION 



Fresh air will flow directly across the 
working place into the gob. 



HAULAGE: 



The change-out is in the second crosscut 
entry. 



:■■ ■■..>: .-.-: 


























LEGEND 



— • Intake Air 

—"■• Return Air 

— s Face Curtain 

■€"~ Check Curtain 

■F- Fly Curtain 

= Stopping 

:fl— Regulator 



(X) Cable Anchor Point 
— Shuttle Car Path 
^7 Discharge Point 
• • • • Roadway /Turn Posta 

: Breaker Posts 
# Cribbing 
Cob 



Split and Fender 
Alternate Cut 24 



HO282021 J Figure 32 



39 



Properties of the Process 

Split and fender is the most commonly used pillar extraction process in 
the United States, primarily because of its adaptability and its simplicity. 
Split and fender is an adaptable process because it works with many different 
pillar sizes. The minimum fender width is generally 8 feet. The minimum 
split width is on the order of 10 feet. The maximum dimensions for width of 
the fenders and splits are approximately 13 feet and 20 feet, respectively. 
This means that it is possible to extract any pillar between approximately 26 
and 46 feet wide using a single split. Wider pillars can be extracted using 
multiple splits, but in doing this, some of the advantages of the basic single 
split technique are lost. More commonly, when a larger pillar is required, 
the pocket-and-wing technique is used for extraction. Pillars of any length 
can be extracted with the split-and-fender process. 

The simplicity of the sequence ensures that the sequence will normally be 
followed and that inadvertent deviations from the sequence will be infrequent. 
However, split and fender generally requires mining two pillars at the same 
time. Changeout points are usually one crosscut back from the active pillar, 
causing delays in haulage. Ventilation, particularly when double-splitting 
the air, is difficult. 

Conditions of Usage 

The split-and-fender process is used under a wide variety of conditions 
and with most mining equipment. The process is adaptable to most seam 
thicknesses and has been observed in seams from 40 inches to 25 feet. Split 
and fender can be practiced with conventional mining equipment and virtually 
all continuous miners (including some auger miners) . 

The split-and-fender process can be ideally used only in pillars of the 
specific dimensions discussed previously. Where larger pillars are required, 
the pocket-and-wing method is more appropriate. 

Because of the versatility of the split-and-fender process, discussing the 
conditions under which it may not be the preferred process is more practical 
than discussing the conditions under which it is preferred. Several consider- 
ations could lead to preference of other methods, as follow: 

1. Very large pillars (wider than 45 feet) are difficult to extract using 
split and fender. 

2. Fragile roof may make it desirable to use a process that results in 
more rapid extraction of individual pillars rather than one requiring 
sequencing between multiple pillars. 

3. The use of open ending may be desirable or more effective when using 
conventional mining equipment or under certain conditions. Split and 
fender also can be used with conventional equipment. 



40 



Common Areas of Usage 

Split-and-f ender extraction is the most common extraction process in all 
regions except the following: 

1. Portions of Alabama where conventional mining predominates. 

2. Portions of southern West Virginia and eastern Kentucky where very low 
coal (less than 36 inches) is prevalent. 

3. The Pittsburgh seam in western Pennsylvania and parts of northern West 
Virginia where pocket-and-wing extraction is practiced. 

The specific practices used in each coal seam can be found in appendix A. 

Pocket and Wing 

The pocket-and-wing pillar extraction process (also known as pocket and 
fender or pocket and stump) is used extensively in some areas. The following 
pages will describe the process, its properties, and the conditions of its 
frequent usage. Finally, the areas in which pocket and wing is practiced 
will be identified. 

Description of the Basic Process 

Pocket and wing is a process in which two or more working places can be 
sequenced within an individual pillar. The process is similar to the open 
ending process (see chapter 4) , except that a wing or fender of coal is left 
on the gob side of the pocket to help support the roof. When the pocket is 
completed, the wing can be recovered during retreat from the pocket. 

The following pages illustrate a detailed, step-by-step sequence of cuts 
for a pillar being extracted by the pocket and wing process. The optimum 
pillar dimensions can be determined according to the techniques described in 
the section of chapter 6 entitled "Pillar Dimensioning." Any number of 
pockets can be driven through a pillar depending upon the overall dimensions. 
For simplicity in the discussions that follow, the pillar has been restricted 
to a size requiring only two pockets. 

The pocket and wing method allows two working places within a single 
pillar, thus eliminating long delays caused by sequencing between pillars. 
Changeout points can be located at the active pillar. Ventilation using 
single split air is a simple process. The specific steps in the extraction 
process are shown in figures 33 through 42. 



41 



This figure shows the overall cut sequence for pillar 
extraction using the pocket-and-wing process. 



ROOF SUPPORT: 



Breaker posts are set at all openings to 
the gob. Roadways have been narrowed to 
16 feet. 



VENTILATION: 



This is shown on individual cut illustra- 
tions . 



HAULAGE: 



Change-out points and haulage limitations 
will be discussed on the individual cut 
illustrations . 







iiiaiiiii^: : $v:fr : &fr : x-/ : : : ffi 



n / y 

ft/ 

8/ 7 / 6 / 



h 






1 



■t 

i 

i 






13 |10 

"d in 

15 ! ^ 12 J 















LEGEND 



— » Intake Air 
»~* Return Air 
— • Face Curtain 
-€"" Check Curtain 
-F- Fly Curtain 

:fl— Regulator 






Cable Anchor Point 
Shuttle Car Path 
Discharge Point 
Roadway /Turn Post* 
Breaker Poets 
Cribbing 
Cob 



Pocket-and-Wing 
Overall Cut Sequence 



HO282021 



I Figure 33 



42 



Cut 1 is the first cut of the first pocket. It is 
started on the long side of the pillar. 



ROOF SUPPORT 



Turn posts will be set prior to initiation 
of the cut. 



VENTILATION: 



HAULAGE : 



Airflow is across the face, behind the 
face curtain, and out into the gob. 

The change-out point is at the first 
intersection. 




LEGEND 



— * Intake Air 

— * Return Air 

— . ' Face Curtain 

"6"~ Check Curtain 

•F- Fly Curtain 

'.ft~ Regulator 



(X) Cabla Anchor Point 

Shuttle Car Path 

TJ Discharge Point 
• • • • Roadway /Turn Posts 

*. Breaker Posts 
# Cribbing 
Cob 



Pocket and Wing 
Cut 1 



HO28202 



1 I Figure 34 



43 



Cut 2 is the first cut of the second pocket. It is 
started into the narrow side of the pillar. Roof 
support, ventilation, and haulage characteristics for Cut 
4 are identical to those of Cut 2. 



ROOF SUPPORT 



While Cut 2 is being mined, Cut 1 is being 
roof bolted. Turn posts will be set prior 
to starting Cut 2. 



VENTILATION: 



HAULAGE: 



The check curtain already in the crosscut 
is extended for use as a face curtain. 
Airflow is across the face, behind the 
curtain, and out into the gob. Air volume 
is regulated at the face by the amount of 
opening in the curtains. 

At the start of Cut 2, the miner's tail- 
piece extends into the intersection, 
forcing the change-out points to be 
located at the next crosscut outby. 










— » Intake Air 
•"■* Return Air 
S Face Curtain 
"€- Cheek Curtain 
*F- Ry Curtain 
= Stopping 
:f\— Regulator 



LEGEND 



(X) Cable Anchor Point 

Shuttle Car Path 

^ Discharge Point 

•••• Roadway /Turn Posts 

, :::*. Breaker Posts 

# Cribbing 
Cob 



Pocket and Wing 
Cuts 2 and 4 



H0282 



021 | Fi 



gure 35 



44 



Cut 3 is the continuation of the first pocket, 
will complete the pocket through to the gob. 



Cut 



ROOF SUPPORT 



As Cut 3 is being mined, Cut 2 is being 
bolted. Breaker posts will be set across 
the opening to the gob after Cut 5 is 
completed. Cut 5 does not have to be 
bolted. 



VENTILATION: 



The brattice curtain is kept within 10 
feet of the face as Cuts 3 and 5 are 
advanced. 



HAULAGE : 



Same as Cut 1. 







tntafca Air 
Return Air 
-^ Faco Curtain- 
€""* Chock Curtain 
F- Ry Curtain 
— — Stopping. 
H— Regulator 



LECCMO 



(X) Cabta Anchor Point 
—- Shuttta Car Path 

^ Oischarg* Point 
••••■ Roadway/Turn Posts 
:::: Breaker Posts 

#T Cribbing. 
Cob 



Pocket and Wing 
Cuts 3 and 5 



HO282021 



Figure 36 



45 



Cut 6 is the first lift from the first wing. Cuts 7 and 
8 complete the first wing. Since the operator is on the 
far side of the miner from the wing, increasing the 
miner's reach, all of the wing can be extracted. 



ROOF SUPPORT: 



Breaker posts are set across the completed 
pocket. Turn posts are set leading into 
each cut. Only the turn posts for Cut 6 
are shown. 



VENTILATION: 



Airflow is into the pocket, across the 
face, and into the gob. It may be 
necessary to use a face curtain on the 
turn posts to direct air into the face. 



HAULAGE : 



Same as Cut 5. 




pfTfT'Bii 










"1 



/lJ_ .- "■' ' 



LEGEND 



— • NitotM Air 

■— * Return Air 

— "* Face Curtain 

"€"• Check Curtain 

•F- Fly Curtain 

—— • Stopping 

:f\= Regulator 



(A) Cable Anchor Point 

Shut 1 1« Car Path 

V Discharge Point 
•*•* Roadway/Turn Posts 

• • . • Breaker Posts 
# Cribbing 
Gob 



Pocket and Wing 
Cuts 6, 7 and 8 



HO282021 



Figure 37 



46 



Cut 9 is the breakthrough cut of the second pocket. 



ROOF SUPPORT 



VENTILATION: 



Breaker posts are set in the entry outby 
the entry pocket and the wing that was 
just completed. Breaker posts will also 
be set across the crosscut pocket when cut 
9 is completed. 

A check curtain is installed outby the 
breaker posts in the entry. The face 
curtain in the pocket is kept within 10 
feet of the face until the cut breaks 
through into the gob. 



HAULAGE : 



Same as Cut 4. 
















~i r 



'■ : 'MXMUtSr 



±T~ 



LEOEMO 



Intake Air 
Roturn Air 
— s Faco Curtain 
€"" Check Curtain 
■F- fly Curtain 
__> stopping 
A— Regulator 



(A) Cabio Anchor Point 

Shuttta Car Path 

TJ Dtachargo Point 
• • • • Roadway /Turn PoaU 



# CHtoMng 
Goto 



Pocket and Wing 
Cut 9 



HO282021 



Figure 38 



47 



Cuts 10-12 extract the inby wing off the crosscut pocket. 



ROOF SUPPORT: 



Cut 10 is started after Cut 9 has been 
completed and breaker posts set. Turn 
posts are set leading into each cut. Only 
the turn posts for Cut 10 are shown. 



VENTILATION: 



For this wing and the next, the miner 
operator is on the outby side of the 
miner, thereby limiting the reach of the 
miner. Airflow is across the face into 
the gob. 



HAULAGE : 



Same as Cut 9. 










"1 




LEGEND 



— * Intake Air 

— » Return Air 

— X Face Curtain 

■6"" Check Curtain 

■F- Ply Curtain 

— Stopping 

:RS Reg u lator 



(X) Cable Anchor Point 
Shuttle Car Path 

^ Discharge Point 
••■• Roadway /Turn Posts 
III: Breaker Posts 

# Cribbing 

; cob 



Pocket and Wing 
Cuts 10-12 



HO282021 



Figure 39 



48 



Cuts 13 and 14 initiate removal of the left (and last) 
wing . 



ROOF SUPPORT 



The opening used for access to the wing 
just finished is sealed off by breaker 
posts. Note that breaker posts are set so 
th t they can also be used for the pushout 
stump. Turn posts are set leading into 
each cut. The turn posts for Cut 13 only 
are shown. 



VENTILATION 



The check curtain, previously located 
across the entry, is removed. A check 
curtain is installed outby the breaker 
posts just set in the crosscut. Airflow 
is similar to that of Cut 8. 



HAULAGE 



The change-out point can be located in the 
intersection. 




LEGEND 



— » Intake Air 

"■"* Return Air 

— -^ Face Curtain 

■€— Check Curtain 

■F- Fly Curtain 

ZZZ Stopping 

LR— Regulator 



(X) Cable Anchor Point 

--- Shuttle Car Path 

^ Discharge Point 

• • • • Roadway /Turn Poata 

'.'.'.'. Breaker Poats 

# Cribbing 

ll§l Cob 



Pocket and Wing 
Cuts 13 and 14 



HO282021 



Figure 40 



49 



Cut 15 is the pushout.. If conditions do not permit the 
use of the entry as a haulageway (as shown here) , the 
crosscut may be used and the entry posted off as shown in 
the next figure. 



ROOF SUPPORT: 



As protection for the roadway leading into 
this lift, breaker posts are set on both 
sides of the roadway. Breaker posts are 
also set in the crosscut outby the 
intersection. 



VENTILATION: 



HAULAGE : 



The check curtain previously hung in the 
crosscut is removed. A check curtain is 
installed in the crosscut. Air passes 
both sides of the pushout and into the 
gob. 

Haulage is restricted to one 14-foot-wide 
roadway. The change-out must be located 
at the second crosscut outby. 




LEGEND 



— * Intake Air 

■""* Return Air 

— ^" Face Curtain 

"€— Check Curtain 

■F- Fly Curtain 

:H— Regulator 



v 



Cable Anchor Point 
Shuttle Car Path 
Discharge Point 
Roadway /Turn Post* 
Breaker Posts 

Cob 



Pocket and Wing 
Cut 15 



HO282021 



Figure 41 



50 



If access to the pushout through the entry is not 
possible, the crosscut may be used as shown in this 
figure. 



ROOF SUPPORT: 



The roadway into the pushout is protected 
by a double row of breaker posts on each 
side. Breaker posts are also set across 
the entry. 



VENTILATION; 



A check curtain is hung in the entry outby 
the breaker posts just set. Air flows by 
both sides of the pushout stump and into 
the gob. 



HAULAGE : 



A single 14-foot wide roadway leads into 
the pushout. The change-out must be 
located at the second crosscut back. 




1 



«&&»•<£* :.?*<:•./ -^ ^ ■■■..■■'.. 



l± 




LCCjMO 



— * Intake Air 
■— *■ Return Air 
— X Face Curtain 
-€— Cheek Curtain 
■F- Fly Curtain 

^.". T>»n.i !■■■■ 



(A) Cable Anchor Point 
— Shuttla Car Path 
^7 Discharge Point 
•••• Roadway /Turn Posta 

Braakar Poata 
# Cribbing 



Pocket and Wing 
Alternate Cut 15 



HO282021 | Figure 42 



51 



Properties of the Process 

There are several important properties of the pocket-and-wing extraction 
process. The first is its adaptability to large pillars. Most of the other 
pillar extraction processes have limitations on the maximum width of the 
pillar. State regulations sometimes limit the maximum dimensions for pillar 
design, but the regulated maximum dimensions are usually greater than the 
maximum pillar dimensions necessitated by equipment limitations. Pocket-and- 
wing extraction is applicable over a wide range of sizes if large pillars are 
necessary or are preferred. 

The second property is the ability to sequence cuts within the same 
pillar. This allows a greater concentration of working places than with most 
other processes. The sequence of cuts for removal of a single pillar rather 
than sequencing cuts between a number of pillars is often preferable because 
of the shorter exposure time within a particular pillar. 

Another property of the pocket-and-wing process is that the operations 
take place from two different entries. This provides protection by having a 
solid pillar outby the pocket at all times. 

Ventilation with the pocket-and-wing process is easier than with the 
split-and-fender process. In areas where the use of double-split ventilation 
is difficult, this property is quite a benefit. 

Haulage with the pocket-and-wing process is also easier than with the 
split-and-fender process. The changeout points can normally be located at 
the pillar rather than one crosscut outby. This reduces delays in mining. 

Conditions of Usage 

Pocket-and-wing extraction is adaptable to virtually all conditions. 
Currently, its use is limited primarily to areas of deep cover where large 
pillars are necessary for support. It has also been utilized in areas where 
roof conditions do not permit long exposure times. An important design 
consideration in any mine plan is to select a process that will provide for 
rapid extraction of a pillar once recovery has begun. Pocket and wing may be 
the best choice in conditions where time within a pillar is very limited. 

Another reason for the use of pocket and wing is the preference of the 
mining company. Initially, pocket and wing may have been chosen as the best 
method known at that time. Pocket and wing may have been introduced as a 
modification of the open-ending plan used with conventional equipment as 
mines converted to continuous mining equipment. Its success has continued 
its use even though the conditions may have changed to the point where 
another method would be superior. 



52 



Pocket and wing may not be desirable if the character of the coal is such 
that energy storage occurs from great pressure concentrations (such as from 
overburden, poor pillar design or alinement, or multiple seam mining) , pro- 
ducing bump conditions. Energy releases in these pillars usually occur along 
the long side of the pillar, where miners frequently work during pocket-and- 
wing extraction. Specific techniques to be employed under bump conditions 
are discussed in chapter 6. 

Areas of Usage 

The Pittsburgh seam in western Pennsylvania and northern West Virginia is 
the principal area where pocket-and-wing extraction is used. It is also 
found in areas scattered throughout Pennsylvania. Detailed information on 
other areas can be found in the appendix. 

Outside Lifts 

The pillar extraction process of mining outside lifts is formally used by 
only a few mines in the country. However, it is a good technique for extrac- 
tion of room pillars and is also used extensively in partial pillar extrac- 
tion. 

Description of the Basic Process 

The outside-lift extraction process is primarily utilized to extract 
long, thin pillars (on the order of 20 by 50 feet). The cut sequence is 
similar to that required to remove the fenders or wings of the processes 
discussed earlier. While more roof bolting is required during the develop- 
mental phase, the retreat phase requires no roof bolting at all. This frees 
the crew to handle timbering requirements, allowing for a smoother work 
cycle. This technique cannot be used for the extraction of chain pillars 
because mining conditions are unlikely to permit leaving 20-foot-wide pillars 
for any substantial length of time. A typical application of this process 
would be in the extraction of small production pillars created when rooms are 
driven to the side of a panel (with the larger chain pillars extracted using 
split and fender or pocket and wing) . The specific steps in the extraction 
process are shown in figures 43 through 47. 



53 



The overall sequence of cuts tor pillar extraction by 
taking outside lifts is shown below. 



ROOF SUPPORT: 



Breaker posts have been set at all 
entrances to the gob. 



VENTILATION: 



This is shown on individual cut illustra- 
tions. 



HAULAGE: 



Change-out points and haulage limitations 
are discussed on the' individual cut 
illustrations . 







riniiwMiiiiimy * j« • * y * v * ■ •' 



f 



— * Intake Air 
■— * Return Air 
S Face Curtain 
■€"• Chech Curtain 
-F- Fly Curtain 
_ stepping 
:ft= Regulator 



LECCNO 






Cibw Ancnoc l^Mftf 
Shuttle Car Path 
Discharge Point 
Roadway /Turn Post* 
Breaker Post* 
wraoomg 
Cob 



Outside Lifts 
Overall Cut Sequence 



HO282021 



Figure 43 



54 



Cut 1 is the first lift. 



ROOF SUPPORT 



Prior to initiating the cut, a row of turn 
posts should be placed leading into the 
lift. 



VENTILATION; 



Airflow is through the entry and into the 
gob. It may be necessary to place a face 
curtain on the turn posts to direct air 
into the cut. 



HAULAGE; 



The change-out can be located at the first 
intersection. 







LECCMO 



— * intak* Air 
— • Return Air 
— X Fact Curtain 
"€- Check Curtain 
•F- Fly Curtain 



® 

— - Shut 1 1* Car Path 

V Discharge Point 

• • • • Roadway /Turn Poata 

f.:: Breaker Poata 

# Cribbing 

i Gob 



Outside Lifts 
Cut 1 



HO282021 



Figure 44 



55 



Cuts 2 and 3 extract the bulk of the pillar. 



ROOF SUPPORT: Turn posts are set across the entry prior 

to starting each cut. Turn posts are 
shown for Cut 2 only. 



VENTILATION: 
HAULAGE: 



Same as Cut 1. 
Same as Cut 1. 




LEGEND 



Intaka Air 
Return Air 
— <^ Faca Curtain 
6~ Check Curtain 
F- Fly Curtain 
__ flopping 
H— Regulator 



(X) Cabla Anchor Point 
Shut 1 1* Car Path 

^ Discharge Point 
•••* Roadway /Turn Posts 
. • . . Breafcar Posts 

# Cribbing 
Cob 



Outside Lifts 
Cuts 2 and 3 



HO282021 



Figure 45 



56 



Cut 4 is the pushout lift of the pillar 



ROOF SUPPORT: 



Breaker posts are set on both sides of the 
roadway leading to the pushout and across 
the crosscut, outby the intersection. 



VENTILATION: 



The check curtain in the crosscut inby the 
intersection is withdrawn. A check 
curtain is installed in the crosscut outby 
the intersection and breaker posts. 



HAULAGE : 



Haulage is limited to one 14-foot-wide 
roadway through the entry. The changeout 
point is located in the second inter- 
section outby the pillar. 




— • Intake Air 
•—■* Return Air 
—•" Face Curtain 
"€— Chacfc Curtain 
-F- fly Curtain 
Z^ZT Stopping 



LEGEND 



V 



Shuttle Car Path 

Discharge Point 

Roadway /Turn Post* 

Breaker Poata 

Ci 

Gob 



Outside Lifts 
Cut 4 



HO282021 



Figure 46 



57 



In the event that the entry is blocked for some reason 
such as a roof fall, an alternative path through the 
crosscut may be required. This is shown below. 



ROOF SUPPORT: 



VENTILATION: 



Breaker posts are set on both sides of the 
roadway leading to the pushout and across 
the entry outby the intersection. 

The check curtain in the crosscut outby 
the intersection is withdrawn, and a check 
curtain is installed in the entry outby 
the intersection. 



HAULAGE: 



Haulage is restricted to the crosscut inby 
the intersection. The change-out must be 
one crosscut outby the pillar. One 
14-foot-wide roadway leads into the cut. 







r 



— ♦ Intake Air 
•— * Return Air 
— * Face Curtain 
■6"" Check Curtain 
-F- Fly Curtain 
ZZT Stopping 
:R— Regulator 



LEGEND 



(A) Cable Anchor Point 
Shuttle Car Path 

^7 Discharge Point 

Roadway /Turn Posts 

"." Breaker, Posts 

# Cribbing 

I!!! Cob 



Outside Lifts 
Alternate Cut 4 



HO282021 



Figure 4 7 



58 



Properties of the Process 

The primary property of the outside-lift process is its suitability for 
small pillars in which lifts need not be bolted. The advantage is that a 
bolting machine and crew are not generally required during retreat operations 
except for spot bolting. This eliminates the need to sequence the miner and 
bolter between two or more places, therefore reducing the time it takes to 
extract a pillar. In addition, this also concentrates most of the operation 
within one area, making it easier to manage. Complete extraction can usually 
be attained since the continuous miner can extract the whole pillar in a 
quick series of small moves. The only delays are for setting timbers for the 
operator's protection. 

Conditions of Usage 

In general, since the process is limited to small pillars, only areas of 
low cover not requiring large pillars can utilize outside lifts. However, 
this process has been used under very deep cover where small, yieldable 
pillars are desired (such as in bump-prone areas) . 

The pillar extraction plan permits relatively quick recovery, thereby 
allowing its use where roof conditions are competent for only short periods 
of time. The process generally allows the miner to get into the pillar, mine 
it out with only a few short interruptions, and get out before any problems 
or dangerous conditions develop. 

Areas of Usage 

The outside-lift process is used in some mines scattered throughout the 
Appalachian coalfields. It is generally (but not always) found in mines 
having low cover that permits the safe use of small pillars. Locations in 
which outside lifts are used are the Pocahontas No. 3 seam in southern West 
Virginia and the Freeport seams in northeast West Virginia and west-central 
Pennsylvania. More detailed information concerning specific areas of usage 
can be found in the appendix. 

Open Ending 

The open-ending pillar extraction process is still used by quite a few 
mines throughout the country. This process is used in mines that utilize 
conventional mining equipment, although not all conventional mines practice 
open ending. 

Description of the Process 

Open ending is a pillar extraction process in which a sequence of cuts is 
taken from one or more sides of a pillar. Since the process is used with 
conventional mining, the same cut is mined from each pillar in the pillar 
line to provide the necessary working places. Figures 48 through 57 show the 
cut sequence for only one of the pillars in the pillar line. The numbers 
indicate the order of cuts taken within the pillar, not the actual cut 
sequence as in the other processes described. 



59 



The overall cut sequence for pillar removal using the 
open-ending process is shown below. Conventional mining 
equipment is utilized and a 45-degree angled pillar line 
is used; therefore, sequencing will take place 
simultaneously in all pillars on the pillar line. 



ROOF SUPPORT: 



Breaker posts have been set at all 
openings to the gob. All roadways have 
been narrowed to 14 feet. 



VENTILATION: 



Shown on individual cut illustrations. 



HAULAGE: 



Change-out points and haulage limitations 
will be discussed on the individual cut 
illustrations. 




LEGEND 



— • Intake Air 

— ■* Return Air 

=W Face Curtain 

-6— Check Curtain 

-F- Fly Curtain 

n3T Stopping 

:ft— Regulator 



(X) Cable Anchor Point 

-— - Shuttle Car Path 

^ Discharge Point 

Roadway /Turn Posts 

I".: Breaker Posts 

# Cribbing 



Open-Ending 
Overall Cut Sequence 



HO282021 



Figure 48 



fin 



Cut 1 is the first cut taken from each pillar in tne 
pillar line. In general, this cut may be cut, drilled, 
and shot while the previous pillar line is being 
finished, but may not be loaded until all the operations 
on the previous pillar line are completed. 



ROOF SUPPORT: 



Due to equipment limitations, general 
practice allows the taking of this first 
cut prior to the placement of the turn 
posts. 



VENTILATION 



HAULAGE: 



A face curtain is hung outby the breaker 
posts. Airflow is through the entry, 
sweeping the face, and then into the gob. 

The change-out point can be located at the 
first intersection. 










— • Intake Air 

—"* Return Air 

— X Face Curtain 

"€— Check Curtain 

■F- Fly Curtain 

SS Stopping 

:R~ Regulator 



LEGEND 



(X) Cable Anchor Point 
Shuttle Car Path 

V Discharge Point 
•••• Roadway /Turn Posts 
'.'.'.'. Breaker Posts 

# Cribbing 



Open Ending 
Cut 1 



HO282021 



Figure 49 



61 



Cuts 2 through 6 remove the rear portion of the pillars. 



ROOF SUPPORT 



A row of turn posts is placed across the 
entry after Cut 1 is loaded. The breaker 
posts are kept within 7 feet of the face. 
Only the breaker posts for Cut 2 are shown 
below. 



VENTILATION: 



A face curtain is 
and breaker posts. 
10 feet of the 
advanced. 



hung on the turn posts 

It will be kept within 

face as the face is 



HAULAGE : 



Same as Cut 1. 




LEGEND 



Intake Air 
Return Air 
-X Face Curtain 
£— Check Curtain 
F- Fly Curtain 
= Stepping 
H— Regulator 






Cable Anchor Point 
Shuttle Car Path 
Discharge Point 
Roadway /Turn Posts 
Breaker Posts 
Cribbing 
Cob 



Open Ending 
Cuts 2-6 



HO282021 



Figure 50 



Ckl 



Cut 7 is the first cut in the second .work area of each 
pillar in the pillar line. 



ROOF SUPPORT: 
VENTILATION: 



HAULAGE: 



The entry to the first work area is 
timbered off with breaker posts. 

A check curtain is hung across the en-try 
on the breaker posts just set. Airflow is 
through the crosscut, across the face, and 
into the gob. 

The change-out can still be located in the 
first intersection. 



:*:v' : ->: : : : /;. 



'.■■■■■ ''•'■' ..'■'■■•■'.'. " ■'. :. : 










LEGEND 



— * Intake Air 

— " • Return Air 

— •" Face Curtain 

■€— Cheek Curtain 

■F- Fly Curtain 

=T Stooping 

:H~ Regulator 



(A) Cable Anchor Point 
— - Shuttle Car Path 

^7 Discharge Point 
• • • • Roadway /Turn Poata 

III Breaker Poata 

# Cribbing 
$Hi Cob 



Open Ending 
Cut 7 



Ji0282^ 



7~r 



Ficmr^^ 



63 



Cuts 8-10 complete the left side of the pillar. 

ROOF SUPPORT: After Cut 7 has been loaded, breaker posts 
are set closer to the face and the roof is 
bolted. Turn posts are placed across the 
crosscut lading into the work area. 



VENTILATION: 



HAULAGE 



The face curtain is extended into each cut 
after it has been loaded. Airflow is into 
the work area, across the face, and into 
the gob. 

Same as Cut 7. 









"■:■' ' '■■■■■ ■■'■■■■■■ ■■' ■ :■■.■■■' 




— ► Intake Air 
■"■ ■* Return Air 
—S Face Curtain 
"€"" Check Curtain 
■p- Fly Curtain 
ZZZZ Stopping 
:R— Regulator 



LEGEND 



V 



m 



Cable Anchor Point 
Shuttle Car Path 
Discharge Point 
Roadway /Turn Posts 
Breaker Posts 
Cribbing 
Cob 



Open Ending 
Cuts 8-10 



HO282021 Figure 52 



64 



Cut il is the first cut in the third work area of each 
pillar in the pillar line. 



ROOF SUPPORT 
VENTILATION: 



HAULAGE 



Breaker posts are set in the crosscut. 

A check curtain is hung across the 
crosscut on the breaker posts just set. 
The curtain in the active entry is moved 
to deflect air into the cut. 

The change-out is still located in the 
first intersection. 









■•■.'. :.."■. . : ■ .■ >:.' 









, : ...... . ... ....... 




LEGEND 

► Intake Air 


® 


Cable Anchor Point 




> ' * Return Air 




Shuttle Car Path 




— S Face Curtain 


V 


Discharge Point 


Open Ending 


-€— Check Curtain 




Roadway /Turn Posts 


Cut 11 


-F- Fly Curtain 


.... 


Breaker Posts 




= Stopping 


# 


Cribbing 
Cob 


I 


-R— Regulator 


HO282021 ! Ficjure 53 \ 



65 



Cuts 12-14 complete the extraction of the third work area 
or the pillar. 



ROOF SUPPORT 



Breaker posts will be maintained within 7 
feet of the face. Turn posts are placed 
across the entry, leading into the work 
area, after Cut 11. 



VENTILATION: 



A face curtain is maintained within 10 
feet of the face. 



HAULAGE 



Same as Cut 11. 















■. * • , - : '' 



ifXWvKv: ,; " i ' ■ i*i 




— "" <•• Intake Air 

*-—* Return Air 

— »** Face Curtain 

"€- Check Curtain 

-F- Fly Curtain 

■Z^T Stopping 

• H— Regulator 



LEGEND 



(a) Cable Anchor Point 
Shuttle Car Path 

V Discharge Point 

• Roadway /Turn Posts 
'.'.'.'. Breaker Posts 

# Cribbing 
HHI Cob 



Open Ending 
Cuts 12-14 



HO282021 



Figure 54 



66 



Cuts 15 and 16 reduce the pillar to a single stump. 



ROOF SUPPORT 



Breaker posts will be maintained within 7 
feet of the face. Turn posts will be set 
across the crosscut leading into the work 
area after Cut 15 is loaded. 



VENTILATION: 



A check curtain is hung across the entry. 
The curtain in the crosscut is moved to 
deflect air into the face and is main- 
tained within 10 feet of the face. 



HAULAGE : 



No change. 




— • Intake Mr 
* mm * Return Air 
— • Face Curtain 
-G~ Chack Curtain 
-F- Ply Curtain 
SSZ Slapping 
• pX^ negoteaer 



LECCMO 



(S) Cable Anchor feint 
— Shuttle Car Path 

^ Discharge Point 
■ • • • Roadway /Turn Poata 
:::: Breaker Poata 

# CHbbing 
Gob 



Open Ending 
Cuts 15 and 16 



HO28202 



n 



Figure 55 



67 



Cut 17 is the final cut--the pushout--m each of the 
pillars. Access through the entry as shown is generally 
easier from a logistic standpoint but may not be possible 
due to mining conditions. 



ROOF SUPPORT: 



Breaker posts are set in the crosscut at 
the gob line. Breaker posts are also set 
across the crosscut at the intersection 
since it will not be used during the 
recovery of the pushout stump. 



VENTILATION: 



HAULAGE: 



All curtains inby the intersection are 
withdrawn. A check curtain is hung across 
the inactive crosscut outby the breaker 
posts. 

Haulage during removal of the pushout is 
limited to one entry. A 14-foot roadway 
is provided leading into the pushout 
stump. The change-out point is one 
crosscut outby the pillar. 












.•.a-.'.'*.'. ■.■■*+ 



~<<~:->*-:-*:-<*<:-*^<':-:-+---> 




- --- 




■%■:■&'■:■■£$. 

: "i'i'i'i'!'i'M"i'i't': 



LCCIND 



— * Intake Air 
— * Return Air 
— S Face Curtain 
€— Chacfc Curtain 
•P- Fly Curtain 



ZftS Regulator 



(A) Cable Anchor Point 
Shuttle Car Path 

^T Discharge Point 
•••• Roadway /Turn Poet* 
::*.; Breaker Poet* 

# Cribbing 
Cob 



Open Ending 
Cut 17 



HO282021 



Figure56 



68 



If mining conditions are such that access through the 
entry is not possible, access to the pushout can be 
obtained through the crosscut, as shown here. 



ROOF SUPPORT: 



Breaker posts are set across the crosscut, 
outby Cut 12. Breaker posts are also set 
across the entry which will not be used to 
recover the pushout. 



VENTILATION: 



All curtains inby the intersection are 
withdrawn. A check curtain is hung across 
the inactive entry outby the breaker 
posts. 



HAULAGE : 



Haulage during removal of the pushout . is 
limited to one entry outby the pushout. A 
14-foot roadway is provided leading into 
the pushout stump. The change-out is one 
crosscut outby the pillar. 








. * • k . v * "" ' • ' ' ° * " "■ 



Intake Air 
Return Air 
— y Face Curtain 
€— Chack Curtain 
F- Fly Curtain 



LfOPjO 



ZfCZ Regulator 





— Shuttle Car Path 
V Discharge Point 
• • • • Roadway /Turn Posts 
:::: Breaker Posts 
# Cribbing 



Open Ending 
Alternate Cut 17 



HO282021 Figure 57 



69 



Properties of the Process 

Open ending has been used successfully by many mines in the past and is 
still successful in the mines using it. The process has a number of advan- 
tages. It is usually not limited by the size of the pillar. Working places 
are always next to the gob, and there i^ always solid support outby the 
working place. 

Conditions of Usage 

The size of the pillar is usually not a limiting condition for using open 
ending, although small pillars could probably be extracted more easily with 
split and fender. Under good conditions, the roof should be competent enough 
to span the pockets driven the length of the pillar yet brittle enough to 
permit breaking off beyond the breaker posts where the pressures would 
otherwise start bending the roof material. The roof should also give 
adequate warning of increasing pressures and should break along relatively 
predictable lines. The coal should not slough excessively since sloughing 
increases the span beyond safe limits. In addition, the coal should have 
enough strength to safely support the roof over working places and entries or 
crosscuts if properly timbered. The floor should also provide the necessary 
support. Open ending can be used under conditions less desirable than these, 
although some coal may be left in stumps near the end of the pockets. 

Open ending is used only with conventional mining equipment. The process 
can be practiced with most methods and conditions of mining although it may 
not be the most desirable economically. 

Areas of Usage 

Open ending is most commonly practiced in MSHA District 7. The process 
is used fairly commonly in Tennessee and Alabama, in the Sewanee, Blue Creek, 
and Pratt coal seams. Each seam has a hard shale (slate) or sandstone roof 
and a clay or shale floor, generally in faulted areas where the seam thick- 
ness varies. Other mines utilizing open ending are scattered in seams 
throughout MSHA Districts 4, 5, and 7, near the eastern edge of the coal- 
fields in southern West Virginia, western Virginia, and southeastern 
Kentucky, respectively, where the strata are generally folded and faulted. 
The coal seams in these areas vary in thickness, and conventional mining is 
advantageous and usually preferred. More detailed information concerning 
specific areas of usage can be found in the appendix. 



70 



Chapter 5. BASIC RETREAT METHODS OF PANEL DEVELOPMENT AND EXTRACTION 

In chapter 4, the basic processes for extracting individual pillars were 
presented. This chapter will present a similar discussion related to the 
three basic retreat methods for the development and full pillar extraction of 
production panels. Prior to reading this chapter, the mine engineer should 
review the information provided in chapter 2, Summary and Comparison of 
Mining Techniques. Following this review, the selection for careful study of 
one or two of the methods presented in detail in this chapter should be 
possible. 

Discussions include the conditions under which each method is effective 
and the areas where it is used. The ventilation and haulage requirements for 
each method will also be presented in detail. 

The three basic methods that will be presented are as follows: 

1. Full extraction on retreat. 

2. Rooms driven and extracted on retreat. 

3. Rooms driven and extracted on both advance and retreat. 

The "rooms only" method discussed in chapter 2 does not involve retreat 
mining and will not be discussed in detail in this manual. 

Full Panel Extracted on Retreat 

The full panel extracted on retreat method involves (1) the development 
of a production panel consisting of five or more entries and (2) the subse- 
quent extraction of the resulting pillars while withdrawing from the panel. 
The overall sequence of panel development and extraction is as follows: 

1. Panel Development. The entries are developed to the limit of the 
panel. As development occurs, haulage must be advanced and permanent 
stoppings must be maintained up to and including the third crosscut 
outby the working face. 

2. Bleeder Connection. When the end of the panel is reached, provisions 
must be made to bleed gases from the area prior to second mining. 

3. Pillar Extraction. As equipment is withdrawn from the panel, the 
pillars are extracted in a manner that results in caving of the main 
roof. 

These operations are performed sequentially and are illustrated in 
figures 58 through 7 2. The panel shown involves an interconnected bleeder 
system with a standing panel bleeder entry. For discussion of other panel 
bleeder designs see the material presented in chapter 6, Mine Planning and 
Retreat Mining. 



71 



The example shown in this and subsequent drawings 
illustrates a seven-entry panel developed during the 
advance. It will be expanded to eight entries during 
retreat by mining through the barrier pillar between the 
active panel and the previously mine adjacent panel to 
the right. The particular method for extraction of the 
barrier block is not part of the Full Extraction on 
Retreat method. It is, however, illustrative of a 
technique that can be incorporated with this and other 
panel extraction methods. Caving is assumed to be tight 
enough to require leaving a row of bleeder blocks in each 
panel during retreat mining. The figure below shows the 
panel as development is completed. The panel contains 
two intakes, two returns, and three 
entries. Haulage is located in entry 4. 
series of illustrations, a regulator will 
first crosscut outby the discharge point, 
a stopping with a block or two missing in order to 
maintain airflow from the haulage entry directly into the 
panel returns. 



neutral intake 

Throughout this 

be shown in the 

This is merely 



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LEGEND 



— » Intake Air 

— ■* Return Air 

— S Face Curtain 

■£— Chech Curtain 

•F- Ply Curtain 



:ft— Regulator 



V 



Cable Anchor Point 
Shuttle Car Path 
Discharge Point 
Roadway /Turn Posts 
Breaker Posts 
wmomg 
Cob 



Full Extraction on Retreat 
Panel Development 



HO282021 



Figure 58 



72 



Once pane 
connected 
the last 
bleeder e 
the bleed 
fall or o 
the entr 
inby the 
into the 
heavily c 
roof fall 



1 development 

to the bleed 

two crosscut 

ntries. A mi 

er system to 

ther obstruct 

ies. Breaker 

third crosscu 

bleeder en 

ribbed to pr 

s. 



is completed, t 
er system. The 
s of the panel b 
nimum of two ent 

keep it operati 
ion limits the a 

posts are set a 
t to prevent fal 
tries. The bl 
ovide protection 



he active 

figure bel 
eing utili 
ries are 
onal in cas 
irflow in 
cross the 
Is from rid 
eeder entr 
against cl 



panel is 
ow shows 
zed for 
used in 
e a roof 
one of 
entries 
ing back 
ies are 
o s u r e by 



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DE 

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— » Intake Air 

"""• Return Air 

— y Face Curtain 

■G— Cheek Curtain 

-F- Fly Curtain 

^ZZ Stopping 

lR— Regulator 



LEGEND 



(a) Cable Anchor Point 
Shuttle Car Path 

^ Discharge Point 

Roadway /Turn Posts 

'.'.'.'. Breaker Poets 

# Cribbing 

W& Cob 



Full Extraction on Retreat 
Bleeder Connection 



HO282021 



I Figure 59 



73 



Before pillar extraction commences in the panel, at least 
three crosscuts must be driven through the barrier pillar 
to provide access to the bleeder entry of the previous 
panel. For each succeeding row of pillars, only one 
crosscut will be mined through the barrier pillar. There 
should be one open crosscut outby the pillar line to 
provide a second escapeway from the pillar adjacent to 
the gob. Pillar extraction can commence after crosscuts 
are completed through the barrier pillar. Pillars are 
extracted from the gob side towards the solid side of the 
panel. The pillar line shown below contains seven 
pillars: five from the active panel, one from the 
barrier pillar, and one from the previous panel. The 
pillar adjacent to the return is left standing to ensure 
proper ventilation of the gob. It will become pillar 
number 1 during the extraction of the next panel. The 
ventilation and haulage positions shown are the positions 
taken as the panel is prepared for extraction of the 
first pillar row. 



untrnnQE 

BnHatlnt 

□ □□□□ 

DDDD 

a 






— -* Intake Alr 
> ■ Return Ahr 

* Face Curtain 

t Cheek Curtain 
-#*— Ply Curtekr 



itcwo 



® 

— Shuttle Car Path- 
V Discharge Point 
• • • • Roadway /Turn Posts 
:*.:: Breaker Poets 
# Cribbing 
Gob 



Full Extraction on Retreat 
First Pillar Row 



HO282021 



Figure 60 



74 



After the first rows of pillars have been extracted, the 
procedures shown in the following drawings will be 
repeated. The figure below shows a typical pillar line 
in the panel displaying the order in which the pillars 
should be extracted. 



□□□□□□□□: 



□□□□□ 

DDDD 
□ 





UCfMD 



— » Intafca Air 
"— • Itaturn Air 
— <" P«ca Curtain 
■£- Chacfc Curtain 
•F- Ply Curtain 



=*= 



(X) Cabto Anchor Point 
— - Shutflfi Car Path 

V Dlacharga Point 
• • • • Roadway/Turn Poata 
I'.'.*. Braafcar Poata 

# Cribbing 
Wt Cob 



Full Extraction on Retreat 
Typical Pillar Row 



HO2820 



21 I Figure 61 



75 



Pillar 1 is the pillar left from the previous panel to 
protect the bleeder entry. This pillar may be inacces- 
sible because of deterioration of conditions since the 
previous panel was developed. 

ROOF SUPPORT: Breaker posts are set across all 
openings to the gob. 



VENTILATION: 



HAULAGE: 



Check curtains are hung across all 
openings in the pillar line to the 
gob. A check curtain is loosely hung 
in the first open crosscut to force 
the bulk of the ventilation across the 
active face. 



Two independent haulage pa 
shown with the change-out loc 
the second intersection ou 
pillar. Trailing cable ancho 
are optimally located for t 
shown. Use of the long-standi 
from the previous panel may be 
if significant deterioration h 
place. This would require an 
tive haulage path. 



ths are 


ated at 


tby the 


r points 


he paths 


ng entry 


limited 


as taken 


alterna- 




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D 

□ □ not 

nnnn 




LEGEND 



— » Intake Air 

— * Return Air 

— ' Face Curtain 

"€"" Check Curtain 

■F- Fly Curtain 

^T Stopping 

:rl— Regulator 



(X) Cable Anchor Point 
--- Shuttle Car Path 

^ Discharge Point 
• • • • Roadway /Turn Poats 
'.'.'.'. Breaker Potts 

# Cribbing 
Cob 



Full Extraction on Retreat 
Pillar i 



HO282021 



Figure 62 



76 



The second pillar in the line can be extracted in a 
manner similar to the first pillar using most of the 
pillar extraction processes. Using the split and fender 
process, however, it will be necessary to initiate double 
split face ventilation as shown below and as explained in 
the detailed discussion in Chapter 4. 



ROOF SUPPORT: 



VENTILATION: 



HAULAGE: 



Breaker posts are set at all openings to 
the gob. Turn posts are set leading into 
all splits. 

The curtain placement shown results in 
return air from the second pillar venting 
into the return. The return air from the 
first pillar will sweep the gob and then 
flow into the bleeder. The alternative 
ventilation plan shown in the next figure 
may have to be used under, some mining 
conditions. 

Haulage paths and anchor points are 
optimum as shown. Obstructions may 
necessitate the use of other paths. 



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HDnnpd 

nnnnnn 



n 



— ► Intake Air 
"""• Return Air 
_ y Face Curtain 
■€-" Cheek Curtain 
•F- Fly Curtain 
ew Stopping 
:f\— Regulator 



LEGEND 



(X) Cable Anchor Point 

- — - Shuttle Car Path 

^ Discharge Point 

•••• Roadway /Turn Posts 

'.'.'.'. Breaker Posts 

# Cribbing 

111 Cob 



Full Extraction en Retreat 
Pillar 2 



HO282021 



Figure 63 



77 



Under conditions where the gob is very compact or falls 
very close to the pillar line and significant airflow 
through the gob is not possible, use of a plan such as 
that shown below would be necessary in order to initiate 
double-split face ventilation. In this plan, the curtain 
arrangement of the first pillar is such that return air 
from it vents directly into the old return from the 
previous panel. A plan such as this would have to be 
used throughout this pillar extraction sequence; however, 
it will be shown only for the number 1 and 2 pillars. 
Its adaptation to the rest of the line is not difficult. 



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3 ; n 

Ti — ilrn i — 1 1 — i Fiti — if 

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•> 



nullil 

□]DI 

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LEGEND 



— * Intake Air 

— ■* Return Air 

S Face Curtain 

■€— Check Curtain 

•F- Fly Curtain 

= Stepping 

;fl— Regulator 



(A) Cable Anchor Point 
-— - Shuttle Car Path 

^ Discharge Point 
• • • • Roadway /Turn Posts 
'.'.'.'. Breaker Posts 

# Cribbing 
IIH Cob 



Full Extraction on Retreat 
Pillar 2 (Alternative) 



HO282021 



Figure 64 



78 



Pillar 3 is shown below. Pillars 1 and 2 are shown tc be 
mined out and part of the gob. 

ROOF SUPPORT: Breaker posts are set at all openings to 
the gob. 



VENTILATION: 



HAULAGE: 



A check curtain is loosely hung in the 
last crosscut to direct the airflow by the 
working place and into the gob. This 
curtain is best located at pillar 4 where 
preparations are taking place for the 
alternate cuts in this sequence. 

Two independent haulage paths are shown 
outby the pillar being extracted. 



c 



Jj&j;itiiMi«vi:iy 




► fotetoc Mr 

— * Fan Cartel* 
-f - Wy Ci'telii 



=H= 



(X) Cable Anchor Point 
— Shuttte Cor Path 
V Dtochorgo Point 
•••• Roadway /Turn Posts 



Cab 



Full Extraction on Retreat 
Pillar 3 



HO282021 



Figure 65 



79 



Pillars 3 and 4 are shown below. Pillars 1 and 2 are 
shown to be mined out and part of the gob. 



ROOF SUPPORT: 



VENTILATION: 



HAULAGE : 



Breaker posts are set at all openings to 
the gob. 

As the split is initiated in pillar 4, the 
check curtain that was in the crosscut 
between entries 5 and 6 is converted to a 
face curtain. This allows double split 
face ventilation once more. 

Independent haulage paths with the change- 
out in the second open crosscut are shown. 
Shuttle car anchor points have not yet 
been moved. 



.'■:. -.-. ■ .. '.'•'■; ■'■■■■':■'■'■■'■ 







n 



3 : 

DUCT 



DD □ 

nana 

nnnn 






IEGCMD 



— * Intafc* Air 
— * Raturw Air 
==^ Vac* Curtate 
■€— Chock Curtate 

»*- Ptu Ch 



-up 



(X) Cable Anchor Point 
Shuttle Car Path 

'^J Discharge Point 
• • • • Roadway/Turn Posts 
til: Braahor Pests 

# Cribbing. 
siHH Cob 



Full Extraction on Retreat 
Pillar 4 



HO282021 Figure 66 



80 



Pillar 5 is shown below. Pillars 1 through 4 are Fhown 
to be mined out and part of the gob. 

ROOF SUPPORT: Breaker posts are set at all openings to 
the gob. 



VENTILATION 



HAULAGE: 



A check curtain is once again hung in the 
open crosscut at the next pillar in the 
sequence. 

To prevent interference from trailing 
cables in the entries during mining of the 
split in pillar 6, the anchor points are 
relocated. A dependent haulage path is 
shown due to the short haul distance. 




nncJQnn 

noaogn 



□i 

In 

n 



— ■* Intake Air 
"—» Return Air 
— X Face Curtain 
■"€— Cheek Curtain 
•F- Fly Curtain 
SSI Stopping 
:f\— Regulator 



LEGEND 



(A) Cabla Anchor Point 
Shuttla Car Path 

^ Discharge Point 
• • • • Roadway /Turn Posts 
:::*. Braakar Posts 

# Cribbing 
Cob 



Full Extraction on Retreat 
Pillar 5 



HO282021 



r» 



igure 6' 



81 



Pillars 5 and 6 are extracted in a manner similar to that 
used for pillars 3 and 4. Pillars 1 through 4 are shown 
to be mined out and part of the gob. 



ROOF SUPPORT 



VENTILATION: 



HAULAGE: 



3reaker posts are set at all openings to 
the gob. 

The curtain placement results in double 
split face ventilation similar to the 
ventilation patterns used during the 
extraction of pillar pairs 1-2 and 3-4. 

Independent haulage paths are shown. The 
anchor point locations used for the 
extraction of pillar 5 will allow these 
independent paths. 



o 
□ 



mm. 



-111 

• :••••• > ' ■ MM !;l f .: ' illlllll > 



rfT 




LEGEND 



— * Intake Air 

■"■"► Return Air 

— * Face Curtain 

■€"" Check Curtain 

■F- Fly Curtain 

= Stopping 

:R— Regulator 



(A) Cable Anchor Point 
--- Shuttle Car Path 

^ Discharge Point 
•'«.*• Roadway /Turn Post* 
:::: Breaker Posts 

# Cribbing 
Cob 



Full Extraction on Retreat 
Pillar 6 



H02 8 



2021 1 Figure 68 



82 



Pillar 7 is the final pillar in the pillar line. 
1 through 6 are shown to be mined out and part 
gob. During the extraction of pillar 
lone pillar, sequencing the cuts with 
line or between three pillars instead 
necessary if the split and fender 
Alternatively, the mining of pillar 1 
with cuts through the barrier block. 



Pil] ars 

of the 

7, or any other 

the next pillar 

of two will be 

process is used. 

might be sequenced 



ROOF SUPPORT: 



VENTILATION: 



HAULAGE : 



Breaker posts are set at all openings to 
the gob. 

Return air is restricted to only one entry 
(entry 1) while extracting this pillar. 
Single split ventilation is shown. 

Independent haulage paths are shown with 
the change-out in the second crosscut 
outby. The change-out can be located in 
the first crosscut outby if the stopping 
in the second crosscut is removed. 



□ : i : t" ! : ! : | : | :"i : : : : t":"^ 
: t f ^ f : J *V| / i ' ' ' " t | " l r*t*t**"|; J ' MA" "I J. ' . 11 y >>*■*: 




!□;□□□ 
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DC 



— ► Intake Air 
"~ • Return Air 
— -^ Face Curtain 
-6— Check Curtain 
•F- Fly Curtain 
— . Stopping 
:R— Regulator 



LEGEND 



(X) Cabla Anchor Point 
— - Shuttle Car Path 

^7 Olacharga Point 

Roadway /Turn Poiti 

:*.'.*. Breaker Poeta 

# Cribbing 
$£§1 Cob 



Full Extraction on Retreat 
Pillar 7 



HO282021 



Figure 69 



83 



Below is shown the section configuration following the 
belt move. The discharge point is moved one crosscut 
back. One row of stoppings is removed on both the intake 
and return sides. The regulator in the return stopping 
is moved one crosscut outby its previous location. Check 
curtains are moved to the locations indicated. The 
trailing cable anchor points for the shuttle cars are 
relocated. The next crosscut in the barrier pillar 
should be completed before the removal of the next pillar 
line is begun. The mining of this crosscut (shown below 
with dashed lines) might be sequenced with the mining of 
a pillar split in order to minimize roof bolting delays. 



tu ' : yft |: : :* . ; , ; . ! : l : ; : : . | ^ 




— • Intaha Air 
— • Return Air 
— ** Faca Curtain 
■€- Chech Curtain 

■F- Ply Curtain 



LEGEND 



■* W — "•QMleWM p 



(a) Cabto Anchor Point 
— Shuttle Car Path 
V Discharge Point 

• • • • Roadway /Turn Posts 

• • • • Brsaltsr Posts 
# Cribbing 

Gob 



Full Extraction on Retreat 
Belt Move 



HO282021 



Figure 70 



84 



When mining with conventional equipment, an angled pillar 
line such as that shown below is desirable. Either the 
open-end or split-and- fender pillar extraction methods 
can oe used. with conventional mining, cuts are made in 
all pillars at the same time. Change-out points are kept 
as close to the pillar as possible. Air is regulated by 
closing curtains at working places. The roof support 
requirements for this method were described in the 
previous chapter. 




Btt^jWl 





■ 

■,.:.■■ -vx - 
iin Dn : C 




nnnOuOoaer 
□nan 



n a ante: l 
n an dtp 

nnnmnncx 
inlnnnntnniDL 

nnnnnnl nu 



LEGEND 



— * Intake Air 

"■"•' Return Air 

— X Face Curtain 

■€— Cheek Curtain 

■F- Fly Curtain 

=T Stopping 

:R~ Regulator 



(A) Cable Anchor Point 

Shuttle Car Path 

y Discharge Point 
•••• Roadway /Turn Poata 

'.'. Breaker Poata 
# Cribbing 

iii cob 



Full Extraction on Retreat 
Conventional Mining 



HO282021 



Fiaure 71 



85 



Continuous haulage systems ;re finding increased accep- 
tance in the industry. While some systems can cut 
rectangular pillars, others are limited to a pattern 
similar to that shown below. In both cases, they have 
had only limited success on sections where retreat mining 
is practiced. The difficulties include the irregular 
pillar line which creates pressure points, difficulty in 
ventilation, and the extraction of the center pillars. 
Several pillar extraction sequences have been utilized. 
The sequence described below requires full bolting in the 
splits. The unmined area shown in the center pillars 
designates coal that generally cannot be extracted 
because of high risk of roof fails. 









LEGEND 
Intake Air 


® 


Cable Anchor Point 




Return Air 




Shuttle Car Path 




Face Curtain 


V 


Discharge Point 


€- 


Check Curtain 





Roadway /Turn Post* 


F- 


Fly Curtain 


.... 


Breaker Posts 




Stepping 


# 


Cribbing 


n= 


Regulator 


sin 


Cob ' 



Full Extraction on Retreat 
Continuous Haulage 



HO282021 



Figure 72 



86 



Rooms Driven and Extracted on Retreat 

The rooms-driven-and-extracted-on-retreat method involves the development 
of a production panel of three to five entries to the designated panel length. 
(Four entries are shown in the example.) The panel is then connected to the 
bleeder system. Rooms are developed on one side as the equipment is with- 
drawn. The resulting pillars and the previously developed chain pillars are 
extracted. Normally, the production rooms are driven on narrower centers than 
shown in the example that follows because they will stand for only a short 
period of time. However, for simplicity, the same dimensions are used for 
both the chain and production pillars. Figures 73 through 80 describe the 
method in detail. 



87 



This figure shows the overall pillar extraction 
sequence. Also shown is the posting and cribbing for 
bleeder protection at the top of the panel. 

ROOF SUPPORT: The bleeder connection and the last 
crosscut are timbered and cribbed to 
prevent closure. 



VENTILATION: 



HAULAGE: 



Shown on individual pillar extraction 
diagrams. 

Shown on individual pillar extraction 
diagrams . 



#. ,#, ,#, ,#, ,#, ,#; i 



nnnnnn 

6 






12 3 4 



— * Intafco Air 
—■ • Return Air 
— -y Fan Curtain 
■€— Chack Curtain 
■F- Fly Curtain 
22 Staooina 
:ftz Ragulatsr 



LEGEND 



(A) CaMa Anchor Foint 
— - Shut t la Car Path 

V Dlacharga Point 
*•** Roadway /Turn Posts 
::*.: Broahsr Posts 

# Cribbing 
Cob 



Rooms Extracted on Retreat 
Overall Pillar Sequence 



HO282021 



Figure 73 



88 



The first pillar in the extraction sequence is shown 
below. The extraction sequence is illustrated for 
pocket-and-wing extraction. The sequence for split-and- 
fender extraction shown previously in the "Full Extrac- 
tion on Retreat" section could be easily applied in this 
panel sequence. 



ROOF SUPPORT 



Breaker posts are place at all openings to 
the gob. 



VENTILATION: 



Air is regulated at the faces. Return air 
from the working faces is drawn partially 
across the mined out area and partially 
through the last open crosscut to the 
panel returns in entries 1 and 4. 



HAULAGE: 



Independent haulage paths are possible 
with the change-out in the first outby 
intersection. 



I ' » ' t.. i I T 1 



12 3 4 




II 



jj 



LEGEND 



— ► Intake Air 

—• Return Air 

— s Face Curtain 

^— Check Curtain 

■F- Fly Curtain 

'ZZZ Stopping 

• r\~ Regulator 



(£) Cable Anchor Point 
Shuttle Car Path 

^7 Discharge Point 
•••• Roadway /Turn Posts 
'.'.'.'. Breaker Posts 

# Cribbing 
W§& Cob 



Rooms Extracted on Retreat 
Pillar 1 



HO282021 



J Figure 74 



89 



The second pillar in the extraction sequence is shown. 
ROOF SUPPORT: 



VENTILATION: 



HAULAGE: 



Breaker posts are placed at all openings 
to the gob. 

Return air from the working faces is drawn 
partially through the gob and partially 
through the panel returns in entries 1 and 
4. 

Independent haulage paths are possible 
with the change-out in the first 
intersection. 




' • 






mmz 














LECgMD _ 

— » Intake Air ® CaW * Anchor **** 

— • Return Air Shuttle Car Path 

_ y Faca Curtain V Discharge Point 

■€— Check Curtain •••• Roadway /Turn Poata 

-F- Ply Curtain '.'.:' Breaker Poata 

= Stopping # Cribbing 

:*= Regulator $& ** 



Rooms Extracted on Retreat 
Pillar 2 



HO282021 



Figure 75 



90 



The third pillar in the pillar extraction sequence is 
shown. 

ROOF SUPPORT: Breaker posts are placed across all 
openings to the gob. 

VENTILATION: Return air paths are similar to those 
shown for the extraction of pillars 1 and 
2. 



HAULAGE: 



Independent haulage paths are possible. 



SCO 




nnn^ 









Intake Air 
Return Air 
•mS Face Curtain 
6- Cheek Curtain 
F- Fly Curtain 
— Slopping 
PfZ Regulator 



LECjMD 



(A) Cable Anchor Point 
Shuttle Car Path 

^ Discharge Point 
•••• Roadway /Turn Posts 
'.'.'.'. Breaker Posts 

# Cribbing 
Cab 



Rooms Extracted on Retreat 
Pillar 3 



HO282021 



I Figure 76 



91 



The fourth pillar in the extraction sequence is shown. 
ROOF SUPPORT: 



VENTILATION: 



HAULAGE: 



Breaker posts are placed across all 
openings to the gob. 

Return air from the working faces 
continues to be drawn partially through 
the mine gob, into the bleeder, and 
partially into panel returns in entries 1 

and 4 . 



Independent 
possible . 



haulage paths are 



not 



L-nU I i [__ 



H. l . l . i . i . i . i , ; 




PI 



LEGEND 



— ♦ Intake Air 

— -* Return Air 

S Face Curtain- 

■€"" Check Curtain 

■F- Fly Curtain 

ZZ2 Stopping 

:R— Regulator 



(A) Cable Anchor Point 
Shuttle Car Path 

XJ Discharge Point 
■••• Roadway /Turn Posts 
".'.:*. Breaker Posts 

# Cribbing 



Rooms Extracted on Retreat 
Pillar 4 



HO282021 



Figure 7" 



92 



The fifth pillar in the extraction sequence is shown. 

ROOF SUPPORT: Breaker posts are placed across all 
openings to the gob. 



VENTILATION: 



Return air from the working faces 
continues to be drawn partially through 
the gob, into the bleeder, and partially 
into panel returns in entries 1 and 4. 
The inby stopping between entries 1 and 2 
is removed and replaced with a check 
curtain in preparation for mining pillar 
6. 



HAULAGE : 



Independent haulage paths are possible. 
The shuttle car trailing cable anchor 
points are relocated to extract the last 
two pillars in the pillar line. 



'fTT!T7&te'sJP&JJJJ&'-[?&Fs^&'9&FZ^&' 






Intake Air 
'ftatum /Air 
' -Faca CiMtaift 
ChaakiCurtatn 
Fly Curtain 






© 

— •- Snuttla .Car Path 

V Olacbarga Point 

••-— Raadvay/Turn ffoats 



# CrfeMng 



Rooms Extracted on Retreat 
Pillar 5 



HO282021 



Figure 78 



93 



The sixth pillar in the extraction sequence is shown. 



ROOF SUPPORT: Breaker posts are placed across all 
openings to the gob. 



VENTILATION: 



HAULAGE : 



Return air from the working faces 
continues to be drawn partially through 
the gob, into the bleeder, and partially 
into panel returns in entries 1 and 4. 

Independent haulage paths are possible 
with the change-out located at the 
intersections of the second crosscut. 




•/fvWvvv 



: 



j| ||| 



UGCNO 



— ♦ Intake Air 
— • Return Air 
— y Fac* Curtain 
■€— Chech Curtain 
•F- Fly Curtain 



(A) Cabta Anchor Foint 
— Shuttle Car Path 
V Discharge Point 
* • • • Roadway /Turn Posts 

\ Brasher Posts 
# Cribbing 
Cob 



Rooms Extracted on Retreat 
Pillar 6 



HO282021 



Figure 79 



94 



The panel extraction sequence has now been completed and 
the panel is prepared for the development of the next set 
of production rooms. 

ROOF SUPPORT: Standard advance support plan. 

VENTILATION: For this system of mining, a double split 
of air is used to ventilate the section. 



HAULAGE : 



Standard development plan. 












LEGEND 



— ♦ Intake Air 
— » Return Air 
— < Face Curtain 
■€— Check Curtain 
■F- Fly Curtain 






(S) CaMa Anchor Wirt 
— Shuttle Car Path 

V Dlecharge Point 
• • • • Roadway /Turn Poata 
*.::: Breaker Poata 

# CHbbing 
Cob 



Full Panel Extracted on Retreat 
Panel Completion 



HO282021 



1 Fic[ure i J30 B 



95 



Rooms Driven and Extracted on Both Advance and Retreat 

This method involves the development of production rooms on the return 
entry side as the panel is developed. These production pillars are extracted 
as the panel is developed. The completed panel is connected to the bleeder 
system. Production rooms are then developed on the intake side, and the 
production and chain pillars are recovered as the equipment is withdrawn. 
The system, illustrated in figures 81 through 93, uses the same pillar dimen- 
sions for both production and chain pillars. The use of smaller production 
pillars is more common. The particular method for connecting the bleeder, 
the retention of the barrier block, and the use of standing pillars in the 
bleeder entry are illustrative and not always required to perform the method 
being discussed. 



96 



In the "Rooms Extracted on Advance and on Retreat" method, 
pillar extraction is initiated during panel development. 
Rooms will be developed on the return side during panel 
development and the production pillars on the return side 
will be extracted. In the figure shown below, the neck of 
the panel has been developed and rooms driven on the 
return side. The first row of production pillars has been 
left to aid in ventilation, and pillars have been 
extracted on subsequent pillar rows as the panel is 
developed. A row of pillars has also been left on the 
perimeter of the panel for ventilation. Roof support, 
ventilation, and haulage characteristics will be shown in 
the following figures. 



"1 

I I I 

I I II 




C J 

d a 

D D 

□tna 



— ► Intake Air 

—* Return Air 

— * Face Curtain 

"6~~ Check Curtain 

■F- Fly Curtain 

S^ Stopping 

:ft— Regulator 



LEGEND 



@ Cable Anchor Point 
Shuttle Car Path 

V Discharge Point 

Roadway /Turn Posts 

'.'.'.'. Breaker Posts 

# Cribbing 



Rooms Extracted on Advance 
and Retreat 
Panel Initiation 



HO282021 



Figure 81 



97 



This figure shows the pillar extraction sequence for 
pillars while on panel development. 

ROOF SUPPORT: Breaker posts are set at all openings to 
the gob. 

VENTILATION: Shown on individual pillar extraction 
diagrams. 

HAULAGE: Shown on individual panel extraction 
diagrams. 



DDDDD 




cJ i 

don 




LEGEND 



—* Intake Air 
- *• Return Air 
__ y Face Curtain 
■€— Cheek Curtain 
•P- Fly Curtain 



(a) Cable Anchor Point 

Shuttle Car Path 

V Discharge Point 

••*• Roadway /Turn Peats 






# CHbMng 



Rooms Extracted on Advance 

and Retreat 
Pillar Extraction Sequence 



HO282021 



Figure 82 



98 



The extraction of the first developmental production 
pillar is shown. 

ROOF SUPPORT: Breaker posts are set at all openings to 
the gob. 



VENTILATION: In this extraction sequence, air is split 
at the pillar and flows over the mined out 
area and down the panel return. 



HAULAGE: 



Independent haulage paths are used. 



-n n. 



onnnn 
Qfeoano 

D i 

,□ jDQD 



n 






► Intake Air 

"-"■* Return Air 
— — <*" Face Curtain 
■€"" Check Curtain 
-F- Fly Curtain 
^SZ Stopping 
:Jl— Regulator 



LEGEND 



(A) Cable Anchor Point 
Shuttle Car Path 

^ Discharge Point 

• • • • Roadway /Turn Posts 

: Breaker Posts 

# Cribbing 

'•SSsjffi Cob 



Rooms Extracted on Advance 

and Retreat 

First Pillar on Advance 



HO282021 



Figure 8' 



99 



When extraction of the second pillar in the development 
extraction sequence is initiated, only minor changes are 
necessary . 



ROOF SUPPORT 



VENTILATION: 



HAULAGE: 



Breaker posts are placed across all 
openings to the gob. 

Air is split at the pillar and flows 
through the mined out area and down the 
panel return. 

Independent haulage paths are used. 



□ □ 
□ □□ 

□ 4 \ I " % 

nononn 

nnnnnn 



— » Intake Air 
■"■* Return Air 
— y Face Curtain 
"€"" Check Curtain 
■F- Fly Curtain 
ZSZ Stopping 
irl— Regulator 



LECENO 



(X) Cable Anchor Point 
Shuttle Car Path 

^ Discharge Point 
•••• Roadway /Turn Posts 
I* Breaker Posts 

# Cribbing 
$181 Cob . 



Rooms Extracted on Advance 
and Retreat 
Second Pillar on Advance 



HO282021 



Figure 84 



100 






At the end of the panel a bleeder is established. The 
first panel pillar in each row is the pillar adjacenc to 
the developmental production pillars, which are now gob. 
(Once again, the pillar line is mined from gob to solid.) 

ROOF SUPPORT: Breaker posts are set at all openings to 
the gob. 

VENTILATION: Shown on individual pillar extraction 
diagrams. 



HAULAGE: 



Shown on individual pillar extraction 
diagrams. 



U ULi U U U U LJ LJ LJ 

D Q D HKIKmiMMKII 

d I 

DC J 

□ □□ a 
d .d 
n ]Q 
una all 

nnnnfin 




— » Intake Air 
■"■* Return Air 
— y Face Curtain 
■G - " Check Curtain 
•F- Fly Curtain 
Z^ Stopping 
lf\— Regulator 



LEGEND 



(A) Cable Anchor Point 

Shuttle Car Path 

^ Discharge Point 

Roadway /Turn Posts 

'.'. Breaker Potts 

# Cribbing 



Rooms Extracted on Advance 

and Retreat 
Pillar Extraction Sequence 



HO282021 



Fiaure 85 



101 



The extraction of the first pillar on retreat is shown 



ROOF SUPPORT: Breaker posts are set at all openings to 
the gob. 

VENTILATION: Air is split at the pillar and regulated 
with the face curtain. 



HAULAGE: 



Independent haulage paths are used. 



^^^^^^™J *'"*fiii»iiifciBitf***"*Jow'e*i<Weaa 

D Q DGOLTDOD 



lOPD 



□ I 

d □ 

□ □ 

p a, 
a nil 

d d 



ID 



nan 




LEGEND 



— * Intake Air 

— • Return Air 

— * Face Curtain 

^— Check Curtain 

•F- Fly Curtain 

"^Z Stopping 

:R— Regulator 



(a) Cable Anchor Point 
— - Shuttle Car Pith 

SJ Discharge Point 
• • • • Roadway /Turn Posts 
:'.:*. Breaker Posts 

# Cribbing 
Cob 



Rooms Extracted on Advance 

and Retreat 

First Pillar on Retreat 



HO282021 



Figure 86 



102 



The extraction of the second pillar on retreat is ataown 

beio':. 



ROOF SUPPORT: Breaker posts are set at all openings to 
the gob. 

VENTILATION: No change. 



HAULAGE: 



Independent haulage paths are still main- 
tained . 



~ 






uulo 

□□□DmQaooa 

do do 
d J 

□DQD 

£■ D 

Of D 

QE D 




LECENO 



— » Intake Air 

"— "* Return Air 

— S Face Curtain 

"€" Check Curtain 

■F- Fly Curtain 

= Stopping 

:R— Regulator 



(A) Cable Anchor Point 

Shuttle Car Path 

^ Discharge Point 

Roadway /Turn Posta 

'.'. Breaker Posts 
# Cribbing 
Cob 



Rooms Extracted on Advance 
and_ Retreat 
Second Pillar on Retreat 



HO282021 



Figure 87 



103 



The panel extraction sequence 
extraction of the third pillar. 



continues with the 



ROOF SUPPORT: 

VENTILATION: 
HAULAGE: 



Breaker posts are set at all openings to 
the gob. 

No change. 

Independent shuttle car paths are used. 
It is necessary to move the shuttle car 
anchor points. 




I ,t :< i i .nj : t h i i n J E ii mhJ * i.ii. ,;.ij 

DDD 
DQC3 



ODODD 

Qidi 



DQDD 
DE3GD 
iDDDDll 




—* intake AJr 
1 ■ Return Air 
—S Face Curtain 
-€"" Check Curtain 
-F- Fly Curtain 
=TT Stopping 
:R— Regulator 



L£Cci«*U 



(A) Cabla Anchor Point 

— - Shuttla Car Path 

^7 Discharge Point 

Roadway /Turn Po»t* 

*. Breaker Poets 

# Cribbing 

W$k Cob 



Rooms Extracted on Advance 
and Retreat 
Third Pillar on Retreat 



HO282021 



Figure 88 



104 



The panel extraction sequence continues with :he 
extraction of the fourth pillar. 

ROOF SUPPORT: Breaker posts are set at all openings to 
the gob. 

VENTILATION: No change. 

HAULAGE: Independent shuttle car paths are used. 



Q.E 1 

DSEl 

d£3€3 
D 3 

n b 
In m 

nan 




LECENO 



— ► Intake Air 

— ~* Return Air 

— . * Face Curtain 

■£- Check Curtain 

■F- Fly Curtain 

=: Stopping 

:R- Regulator 



(A) Cable Anchor Point 
Shuttle Car Path 

^ Discharge Point 

Roadway /Turn Poatt 

'.'.'.'. Breaker Posts 

# Cribbing 

llll Cob 



Rooms Extracted on Advance 

and Retreat 

Fourth Pillar on Retreat 



HO282021 



Figure 89 



105 



The panel extraction sequence 
extraction of the fifth pillar. 



continues ;;ith 



ROOF SUPPORT: 3reaker posts are set at ail openings to 

the gob. 

VENTILATION: No change. 

HAULAGE: Independent shuttle car .paths are used. 



d 









□ 



□ c □ 

d □ 

a 






□ 

QDDD 



LEGEND 



— * Intake Air 

— "* Return Air 

—^ Face Curtain 

"€~ Check Curtain 

■F- Fly Curtain 

— — S'"PP' p *9 

:f\- Regulator 



(A) Cable Anchor Point 

— - Shuttle Car Path 

^ Discharge Point 

• • • • Roadway /Turn Posta 

'.'.'.'. Breaker Posts 

# Cribbing 

WM Cob 



Rooms Extracted on Advance 
and Retreat 
Fifth Pillar on Retreat 



HO282021 



Figure 90 



106 



The panel extraction sequence continues with the 
extraction of the sixth pillar. 

ROOF SUPPORT: Breaker posts are set at all openings to 
the gob. 

VENTILATION: No change. 

HAULAGE:- Independent shuttle car paths are usee. 




□ E3 
DD CD 
d D 

d h 

1 •'■ : : -:: : : : : : :: ; : : : : : : : x':':':-:-: : :-:v: : ' 

n n 



Di 

and 



LEGEND 



— » 


Intake Air 


>— ♦ 


Return Air 


^ 


Face Curtain 


-€- 


Check Curtain 


-F- 


Fly Curtain 


^^z 


Stopping 


=R= 


Regulator 



(a) Cable Anchor Point 
--- Shuttle Car Path 

^ Discharge Point 

Roadway /Turn Poata 

: ; i: Breaker Poata 

# Cribbing 
Cob 



Rooms Extracted on Advance 
and Retreat 
Sixtn Pillar on Retreat 



HO 



282021 1 Figure 91 



107 



The panel extraction sequence is completed with the 
extraction of the seventh pillar. 



ROOF SUPPORT: 

VENTILATION: 
HAULAGE: 



Breaker posts are set at ail openings to 
the gob. 

No change. 

Independent shuttle car paths can be 
maintained outby the second crosscut. 




□ 




= 



□□□□□ 









ODD 

* I — pp-i * * 

Id 




n n n n 




LEGEND 



Intake Air 
Return Air 
— S Face Curtain 
£— Check Curtain 
F- Fly Curtain 
^Z Stopping 
ft— Regulator 



(A) Cable Anchor Point 
Shuttle Car Path 

V Discharge Point 
•••• Roadway /Turn Posts 
'.'.'.'. Breaker Posts 

# Cribbing 
• Cob 



Rooms Extracted on Advance 

and Retreat 

Seventh Pillar on Retreat 



HO282021 



Fiqure 92 



108 



In preparation for extraction of the next row, a -oom 
entry is driven into the solid coal. 



ROOF SUPPORT: Roof support is in accordance with the 
standard advance minina olan. 



VENTILATION 



HAULAGE: 



Ventilation is in accordance with the 
standard advance mining plan. 

Haulage is in accordance with the standard 
advance mining plan. A r:elt move is 
required prior to initiation of mining. 



p n £~ J Q 6 Q^JQp^O i 

dado DDDDDD 

DEE 

dan 
,noo 

l_tl_] 

nnn 




■I ii ii 
ii ii ii 
ii ii ii 



— ► Intake Air 

"—* Return Air 

— y Face Curtain 

-€~ Cheek Curtain 

-F- Fly Curtain 

ZZZ Stopping 

:R- Regulator 



LEGEND 



(X) Cable Anchor Point 
Shuttle Car Path 

^ Discharge Point 

Roadway /Turn Posts 

*.'.'.■. Breaker Posts 

# Cribbing 

W& Cob 



Rooms Extracted on Advance 
and Retreat 



HO282021 



Figure 93 



109 



Chapter 6. MINE PLANNING AND RETREAT MINING 

In the preceding chapters, the reader has been presented with information 
that will aid in the selection and practice of a panel extraction method and 
pillar extraction process. All of this material, however, has been presented 
under the assumption that the operator has decided that retreat mining is 
desirable and the mine has been designed accordingly. To assist operators in 
making such a decision and mine planners in designing for retreat mining, 
this section addresses two points: whether to retreat mine and how to design 
a mine to allow retreat operations. The first section deals with deciding 
whether or not to retreat mine. Among the factors to be considered are the 
effects of geology, environment, labor, economics, and extent of extraction. 
The second section details those aspects of mine planning affected by a 
decision to retreat mine, including dimensioning of rooms and pillars, 
bleeder systems, and retreat mining and bumps. 

Making the Decision To Retreat Mine 

Geologic Considerations 

The nature of the earth above and below a mine and the nature of the coal 
seam greatly affect the decision to retreat mine. Consideration must be 
given to the overall rock strata; the overburden composition; the mine floor; 
the coal seam; structural geology; the pitch of the coal seam; and multiple, 
overlying, and underlying coal seams. These factors are discussed below to 
highlight points important in retreat mining. 

Rock Strata 

The substance that comprises each stratum of rock in the vicinity of a 
coal seam is one of the major factors determining the strength of the roof 
and floor of a mine, which makes it a key factor in the decision to retreat 
mine. Some common rock types associated with coal seams and their properties 
as they relate to retreat mining are detailed below. 

Coal . — A coal seam may be made up of different beds having somewhat 
different strengths and elastic properties. This can create high internal 
stresses and cause spalling of exposed surfaces when mining. Coal with a 
high ash content is likely to be a dull, dense, strong, attrital coal; a 
bright, shiny coal usually indicates a weak, anthraxylon coal, probably low 
in ash. A luster between bright and dull usually indicates a mixture of the 
two — coal is rarely composed of only one or the other — with a strength lying 
somewhere between their separate strengths. Many coal seams will have two 
fracture planes, the major or face cleavage and the minor or butt cleavage 
which runs perpendicular to the face cleavage. A semibituminous coal may 
have three or more fracture planes, making it a weaker coal. The strength of 
the coal is important in the design of the pillars and also in determining 
the susceptibility of the coal to bumps or bursts. 

Shale . — Shale is found overlying most coalbeds and thus forms the imme- 
diate roof for those deposits. It may or may not be able to- support its own. 
weight. A good rule of thumb is, if a shale roof is 8 feet thick or more, it 
generally will be a good roof. This is because thick shale resists permea- 
tion by water. However, if the shale stratum is thin, particularly if it has 



110 



fractures, moisture can penetrate. Most shale deteriorates with exposure to 
air since it absorbs moisture. The water will reduce the adhesion of the 
shale stratum to the rest of the overburden, which could cause a roof fall. 
The nature of shale makes it a good roof for retreat mining since a clean, 
tight fall can generally be attained. 

Slate . — As commonly used in the coal industry, slate is another term for a 
shale that splits into thin horizontal layers with straight cleavage planes. 
It is of various colors, black, gray, and green being the most common. Black 
slate has a high carbon content and may even approach coal in composition. As 
with other types of roof, slate can be strong or weak and may contain irregu- 
larities. Slate has a tendency to separate from other layers above it, caus- 
ing hazardous conditions. Often it is taken down as the coal is extracted (a 
draw slate) . Generally, it makes a good roof for retreat mining since a clean 
fall can normally be attained. However, extra support measures are required 
during advance mining when a fall is undesirable. 

Draw Slate . — Draw slate is a general term for any shale, fire clay, or 
soapstone that comes down, or must be taken down, after the supporting coal 
has been removed. Draw slate usually contains many slips and cleavages that 
make it very treacherous. Where mining conditions permit, draw slate is 
often deliberately shot or cut down in the mining operation, especially if 
overlain with a better roof stratum. A limit to this practice is imposed by 
the tradeoff between (1) better roof support and mining conditions at the 
face and (2) increased contamination of the coal, which causes higher trans- 
portation, cleaning, and refuse-handling costs. Draw slate is not usually 
advantageous for retreat mining due to its unpredictable fall characteris- 
tics. 

Sandstone (or Sandrock) . — Sandstone often has so much shale in its 
binding material that it is really a sandy shale. If the grains are well 
cemented, sandstone can make a good roof during advance mining; however, 
during retreat, it may be difficult to get the sandstone to break and the 
roof to fall when desired. If the grains are poorly cemented, the reverse 
can be true, with the sandstone making a poor roof for advance operations but 
a good roof during retreat mining. Sandstone is highly porous, which means 
the presence of water can cause the sandstone to lose its adhesion to the 
rest of the overburden, resulting in a hazardous roof condition. 

Bone Coal (or Boney) . — Bone coal is a mixture of shale and coal frequently 
found at the top of a coalbed. Often, when bone coal is at the top of the 
bed, it is used for the roof if the thickness is sufficient to leave it in 
place. It varies in strength with the content of the shale or coal. Gener- 
ally, it has good characteristics for retreat mining, particularly if shales 
are found on top of it. 

Limestone . — Limestone usually has less faulty conditions than other forma- 
tions because of its consolidated nature. Limestone does not often form the 
roof immediately above the coal to be mined; however, it may form the main 
roof. Limestone, like sandstone, may be a poor roof for retreat mining 
because of its massive nature and the resulting difficulty in getting clean 
falls. 



Ill 



Soaps tone . — Soapstone is a varietal mass of impure talc. It may be white, 
gray, or greenish in color. Soapstone seldom has the strength to support its 
own weight and so is a source of many hazards. Soapstone, because of its 
weight and poor adhesion, seldom impedes roof falls, but its instability makes 
it undesirable as an immediate or main roof. 

Fire Clay . — Fire clay is a deposit of mud that time and pressure have 
changed to rock. It ranges in color from white to deep gray and may be inter- 
spersed with coal, bone coal, shale, or sandstone streaks. It may occur over 
the coalbed, in it, or form the floor. For most coal seams, it forms the 
immediate floor. It may be hard and firm, or it may be soft. Usually it 
softens when exposed to air and water, creating muddy conditions. It can 
create hazards when present in the roof because of its poor adhesion to other 
strata and lack of strength. 

Overburden Composition 

Knowledge of the particular deposits making up the overburden is impor- 
tant in deciding whether to conduct retreat mining. The overburden affects 
pillar dimensions, equipment selection, roof control plan, and the selection 
of the mining technique. The overburden should be strong enough, given the 
proper pillar sizes and temporary support, to allow the development work to 
be done safely, yet weak enough to fall at the proper time during retreat 
mining. If this is not the case, variations in the pillaring plan, such as 
increasing or decreasing pillar dimensions or utilizing a different sequence 
of cuts, must be employed; or some other mining method, such as longwall 
mining, must be chosen. It is possible that extracting the pillars by the 
retreat method may be too hazardous or too costly. The overburden composi- 
tion affects safety since a very weak overburden is dangerous and could fall 
prematurely during the pillar extraction process. A very strong overburden 
that does not fall soon after extraction of a pillar fails to relieve the 
pressure upon remaining pillars. This could cause the remaining pillars to 
fail, resulting in a dangerous, unplanned, and massive roof fall, causing 
injuries and the loss of much coal. Overburden composition also affects the 
economics of retreat mining in that either the cost of supporting a very weak 
immediate roof might be prohibitive, the size of the pillars needed to support 
the main roof might be too large (leaving too much coal) to be economical, or 
the cost of caving a very strong overburden might be too high. 

Floor Composition 

The composition of the floor under the coal is another important con- 
sideration. Often the floor consists of a fire clay that varies in thickness 
from a few inches to several feet. In the presence of water, fire clay, which 
might be firm during advance mining, could become mud during retreat mining 
and thus impede the movement of mining machinery. 

The floor of a coalbed is frequently weaker than the roof; therefore, 
decisions concerning pillar size and mining method must be based partly on the 
composition of the floor. This is because the fire clay will have plastic 
flow under too much roof pressure, causing pillars to sink and the floor to 
heave. Further, the settlement of a pillar could cause the load formerly 
carried by that pillar to be transferred to adjacent pillars. When this 
occurs, the adjacent pillars could fail due to excess stress, or the strength 



112 



of the roof material could be exceeded, causing a roof fall. However, a minor 
floor heave could relieve stress in the roof at the rib line and improve roof 
stability. 

Ideal mining conditions exist in mines with firm shale floors and suffi- 
cient yield in the roof, pillars, and floor. But if yield is low and over- 
burden pressure is high (generally, over 1,000 feet of overburden) , extremely 
hazardous conditions can result. Pieces of coal under extreme pressure will 
literally explode out of a block in a phenomenon known as a bump or a burst. 
Conditions such as these call for special mining techniques and are the sub- 
ject of a discussion found later in this chapter. 

Coal Characteristics 

The composition and characteristics of the coal also affect the decision 
to retreat-mine. The physical properties of the coal dictate the value of the 
coal, its mining characteristics, its ability to maintain a rib or support the 
roof, and the type of warning it will .give the miners as they work to extract 
the block. Coal geology and quality can, but do not necessarily, change 
within a specific coalbed. This depends on the original materials forming the 
coal and its exposure to geologic conditions. The coal should have a low 
modulus of elasticity (that is, the ratio of the load applied to the amount of 
deformation) so that the amount of energy released during failure is less and 
warnings of failure are evident. (See discussion of bumps at the end of this 
chapter. ) 

Structural Geology 

Unusual conditions pertaining to structural geology can occur and may 
influence the decision to retreat-mine. Thinning of the coal seam due to 
erosion of the coal and replacement with roof material, downward bending of 
the roof into the coalbed, or upward thrusting of the floor produce areas 
with small amounts of coal (want areas) called rolls or pinches. Sections of 
shale, sandstone, mud rock, or clay are sometimes found cutting through a 
coalbed or the layers of rock on top of the seam, forming rock deposits or 
clay veins. These can cause slip planes that might make retreat mining 
hazardous. 

Pyritic sulfur may occur in coal in the form of nodules or balls from a 
fraction of an inch to several feet in diameter. Sulfur balls impede mining 
and may slow down the rate of extraction of a pillar. Sometimes, oddly 
shaped masses that are not the same as the rest of the rock in the stratum 
are encountered. These may have been formed by mud that was packed into the 
space occupied by an old fallen tree trunk, a fossilized tree trunk, or 
minerals or bones of animals fused together. These formations are often 
referred to as horsebacks, kettle bottoms, or domes and are usually so poorly 
joined to the coal or to the rock in the roof that they may drop out unex- 
pectedly. Special roof control measures may be required if these are 
encountered while mining a pillar. 

Figure 94 shows some of these structures in mine strata. The mine plan- 
ner must determine the existence or possible existence of such structures 
and, prior to making a decision to retreat-mine, ensure that adequate meas- 
ures are taken to control these conditions and that the cost of control in 



113 



terms of dollars and potential hazards is sufficiently low to allow economi- 
cal retreat mining. 

Pitching Seams 

The pitch of a seam can be a factor in determining whether to retreat 
mine. Slight grades increase haulage effort and time and decrease the amount 
of material that can be moved. As grades become steeper (approaching approx- 
imately 10 percent) , standard equipment begins to lose traction. If the 
degree of pitch is too great, tramming of haulage and mining equipment may be 
difficult if not impossible. 

The effects of seam pitch on pillar shape and weight distribution is 
another factor for consideration. A good pillar line is dependent upon the 
distribution of weight upon all pillars in the line. In flat seams, the 
weight of the overburden is symmetrically distributed. But as the degree of 
pitch increases, the weight of the overburden will become asymmetric as shown 
in figure 95. The end of the pillar carrying the most weight may start 
sloughing off and become so weakened as to cause the premature failure of a 
pillar in a pillar line. 

Pitching seams occur in the Rocky Mountain region and in the eastern part 
of the Appalachian region where the coal seams are heavily folded. Folding 
of the strata can weaken them, causing roof problems. Pitching can also 
occur where the coal seam has been disrupted by faults. 



:•'•' Sandstone 



i i ill 

! ' [ ■ Limestone i ' i ' I 
II , I , 1 ' 1 












(_ Kettle 
bottom 



deposit 






Main 
y roof 






Immediate 
roof 



" '■•it; V^fc 



FIGURE 94. - Mine strata with intruding structures. 



114 



Multiple Seams 

Multiple seams of coal can have a significant influence on the decision 
to retreat-mine. If no mining has taken place, consideration must be given 
to the proper order of mining the seams. If mining has taken place in 
another seam, this must be considered. Mining in adjacent seams might cause 
problems in subsequent mining and lead to a decision not to retreat-mine. 

If mining of multiple seams is planned in a virgin coalfield, the proper 
order of mining is generally from top to bottom. This will aid in roof sup- 
port and drainage but may result in the initial mining of a lower quality 
seam, which may affect the economics of the planned mining. It is also 
advisable to mine one seam at a time. Attempting to mine more than one at a 
time can be hazardous, especially when retreat mining, since the shock of a 
fall in one seam could trigger falls in the other. 

Often, however, a decision to retreat-mine must take into account the 
extent of mining in other seams. A lower seam may have been more desirable 
and may have already been mined out. In subsequent mining of the upper seam, 
severe roof control problems may be encountered because of poor alinement or 
because the strata yielded as the lower seam was mined out. If retreat 
mining has been done in the lower seam, conditions are likely to be so poor 
in the upper seam that mining by any method is impossible. 

When mining below a seam that was advance-mined only, alinement of the 
current mining with the previous rooms and pillars is desirable, but the 
mappings of the old works may be so poor that alinement is impossible. In 
some cases where this problem has occurred, remote sensing techniques have 
helped determine the layout of the abandoned workings. However, the degree 
of influence that the mined coalbed has on the unmined bed decreases with 
increased distance between the beds and increases with the thickness of the 
mined seam. The degree of influence is also dependent on the composition of 
the strata between the seams. It may not be possible to mine the seam imme- 
diately below a previously mined seam, but it may be possible to mine other 
seams located deeper within the strata. 

Another factor for consideration is the possible presence of water in an 
overlying mined-out coalbed. After a mine has been abandoned, infiltrating 
water can flood the mine workings. Developmental work in the seam below is 
not likely to disturb the continuity of the strata between the seams, but 
Detreat mining is likely to cause fractures in the strata, which could lead 
to the inundation of the new mine by water standing in the old workings. 

In summary, a decision to retreat-mine must take into account the ques- 
tion of multiple seams. Prior mining of seams might make retreat mining 
undesirable or perhaps even impossible. 

Environmental Considerations 

In the early stages of the decisionmaking process, there are basic 
environmental considerations associated with coal mining that must be 
addressed, including such factors as mine waste disposal, acid mine drainage, 
and reclamation. When retreat mining is being considered, certain other 



115 



factors must be evaluated either in addition to those normally considered or 
in greater detail. Two factors particularly important to retreat mining 
operations and discussed below are subsidence and underground hydrology. 



y " v ;' 




L 



Pillar at a flat pitch 



1 I 1 1 !■ ■ 




Pillar at a dipping pitch 



FIGURE 95. - Distribution of overburden weight. 



116 



Subsidence 



When pillars are removed in the retreat mining process, the overlying 
strata subside into the resulting void. The critical factors related to 
subsidence can best be explained with the help of a two-dimensional model, 
(fig. 96). 



The subsidence profile, or trough, is commonly described in terms of the 
angle of draw, seam thickness extracted, depth of the seam, and width of the 
mined-out area. The subsidence deflection, usually expressed as a percentage 
of seam thickness, increases as the width of the mined-out area increases up 
to a critical opening width, at which point the subsidence deflection reaches 
its maximum. The maximum is often about one-half of the seam thickness. The 
critical width can be determined by projecting two lines at the angle of draw 
down to the coal seam from a point on the surface. 



Surface 



Subsidence deflection 




Angle of draw 
coal seam 



Width of mined-out area 



Depth 



Seam thickness 



FIGURE 96. Two-dimensional model of subsidence. 

In considering the implications of subsidence, it should be understood 
that there are horizontal displacements as well as vertical displacements on 
the surface; such displacements can damage or destroy surface facilities. As 
the surface subsides, horizontal displacement is compressive in the region 
above the opening and is tensile to either side of the opening, as shown in 
figure 97. 



117 



Tensile Zone 


i 
1 
1 
i 


Compressive 
Zone 


i 
I 
i 
i 


Tensile Zone 






fl - Opening <% ■ Ht 





FIGURE 97. - Example of subsidence from underground mining. 



In retreat mining, subsidence must be planned for as opposed to prevented. 
With complete or nearly complete pillar extraction, the top will inevitably 
collapse and subsidence will occur. Subsidence occurs within 1 to 2 days 
after the area has collapsed. Surface facilities located well within the 
limits of a uniformly subsided area may not be damaged. This is because most 
of the damage-causing, ground-length changes occur toward the perimeter of the 
subsided area. When areas are identified where subsidence is not allowable, 
such as under roads or buildings, a significant area below that area must not 
be pillared. This is due to the inverted cone effect of the subsidence area. 
If the surface area where subsidence is not allowed is very large, retreat 
mining might not be practical. 

Underground Hydrology 

Consideration must also be given to the fact that once the overlying 
strata are disrupted, as in roof collapse, there is a greater chance of 
affecting underground hydrology. The fissures and cracks allow surface 
runoff water to more easily permeate the overburden and may create 
pollution-causing acidic effluents. Analysis of the overlying strata prior 
to retreat mining can help to avoid acid-forming situations. Rock fracture 
zones and faults have a strong influence on ground water flow patterns, and 
often the fractures and faults collect and convey large quantities of water. 
Avoidance of these areas by pillaring operations may alleviate serious 
problems. 

A complete hydrogeologic site evaluation to determine aquifer 
characteristics and waterflow systems is necessary before a decision to 
retreat-mine is made, because most underground mines receive water from 
overlying aquifers. The resultant roof collapse from retreat mining could 



118 



severely disrupt the natural aquifer conditions and cause not only polluting 
effects due to acidic mine effluent but also loss of necessary water for 
surface facilities and expensive pumping of water from low areas of the mine. 

Labor Considerations 

Labor is one of the most important issues facing the underground coal 
mining industry and is one of the primary considerations to be evaluated when 
making the decision to retreat-mine. Over the past decade, there has been a 
dramatic redistribution in the age of the work force. Table 3 illustrates 
this shift. As can be seen, the under-30 miners have increased steadily as a 
percentage of the number of workers. In 1975, underground coal miners under 
30 years of age comprised 37.4 percent of the work force, and the figure is 
undoubtedly higher today. The problem caused by this redistribution is that 
much has been lost in the way of mining experience. In general, the older 
miners who have retired have not trained the new, young work force in the art 
of retreat mining operations. Because of this loss of experience, the 
hazards and problems associated with retreat mining will be even greater. 

One of the purposes of this manual is to provide mines having only a few 
laborers experienced in retreat mining with a single source of information on 
the basics of retreat mining. It must be emphasized, however, that learning 
the feel and nuances of retreat mining by reading this or any other document 
is not possible. 

In the process of deciding to retreat-mine, mine management will have to 
determine if it has the desire, ability, and patience to gradually and safely 
develop a retreat mining work force. An experienced retreat mining work 
force is not something that can be created hurriedly or easily. A work force 
with experience in the more basic aspects of advance room-and-pillar mining 
can be trained for retreat mining. A gradual program should introduce the 
method to the most proficient crew and, following initial success, expand it 
to the remaining crews. 

TABLE 3. - Ranking of workers by age groups, 1966-75 





Age group 


1966 


1968-70 


1971-72 


197 3 


1975 


2nd greatest number of workers 

3rd greatest number of workers 

4th greatest number of workers 


Over 50 
40 - 49 
30 - 39 


Over 50 
40 - 49 


Over 50 


Under 30 


Under 30 


Under 30 


Over 50 
30 - 39 
40 - 49 


30 - 39 
Over 50 
40 - 49 


Under 30 


40 - 49 
30 - 39 


Under 30 


30-39 



119 



Economics 

Productivity on a retreat section can be significantly higher under cer- 
tain conditions than on an identical advance section. Even in cases where 
productivity is not significantly higher on retreat, it is rarely signifi- 
cantly lower. Much of the supporting equipment that is required on a retreat 
section will have already been installed while on advance, but part of the 
resultant time saved will be spent installing temporary roof support. 

The economic incentive to retreat mining is a matter not only of reduced 
cost but also of increased recovery. Recovery rates within a panel normally 
average as much as 65 percent for advance-only mining. Panel recovery 
percentages with the use of retreat mining can be as high as 80 percent. On 
a minewide basis, advance-only mining yields about 50 percent, while full 
retreat mining approaches 70 percent. The recovery rates may not have a 
great disparity, but recovery of pillars still yields a significantly greater 
amount of coal. 

The mine engineer must assess the economic impact of retreat mining for a 
particular mining operation. The approach commonly used today is to perform 
an analysis using an econometric model. The model most widely used is a 
discounted cash flow (DCF) model, which allows for the decreased value of 
money over time. 

In considering the possibility of retreat mining, the engineer must 
evaluate several potential advantages, including — 

1. Decreased operating costs (productivity rates and supply costs) . 

2. Increased utilization of reserves (improved recovery rate of coal) . 

3. Extended life of the mine. (For a given acreage, more coal is 
available; thus, at a given production rate, the mine life is 
extended. ) 

The impact of retreat mining upon these parameters — operating costs, reserve 
utilization, and mine life — can be evaluated using the DCF model. Values can 
be assigned to the variables comprising each parameter, some of which may be 
estimated. Each variable may then be tested for its sensitivity to changes 
in the other variables attributable to retreat mining techniques. Any 
economic advantages of retreat mining that are identified will be significant 
in determining the overall profitability of a coal mining venture. 

Mine Planning for Retreat Mining 

Dimensioning of Rooms and Pillars 

The following four factors are generally used to determine the dimensions 
of rooms, pillars, and production panels: 

1. Rock mechanics 

2. Equipment 

3. Ventilation 

4. Historical practices 



120 



The purpose of this section is to give the mine engineer sufficient infor- 
mation to evaluate the requirements of these factors and arrive at optimum 
pillar and panel dimensions. That is, the optimum dimensions are not 
necessarily the best for meeting the requirments of each factor, since one 
requirement may be in opposition to another, but are the best considering the 
requirements of all factors. 

Basic Rock Mechanics Principles 

Mine planners must consider the principles involved in supporting the 
overburden above a coal seam during the advance and retreat phases of mining 
so that these operations are undertaken in the most effective, safe, and 
economic manner possible. These principles should be applied in designing 
openings and pillars in entry sets, in designing rooms and pillars for 
subsequent retreat operations, and in determining appropriate roof support 
operations. 

There are many rock mechanics theories being applied in the industry 
today, some of which appear to conflict and none of which contains the 
solutions to all problems or covers all the necessary considerations or 
potential situations. However, they can be used as guidelines, with the 
results from calculations being modified to suit the specific conditions of a 
particular mine. 

This subsection provides some very basic rock mechanics theories to aid 
in understanding the principles behind entry, room, and pillar design and 
roof support techniques. The theories discussed are pressure arch theory, 
the Voussoir arch, and pillar strength. 

Pressure Arch Theory 

When an opening is driven into a coalbed, the immediate roof bends down- 
ward to free itself of the load from the main roof. The load from the main 
roof (about 1.1 pounds per square inch for each foot of depth) is then trans- 
ferred to the remaining solid coal (abutments) , forming a pressure arch. If 
the width of the opening is progressively increased, the pressure arch 
becomes larger and larger until the roof breaks; after this point is reached, 
the weight of the overburden will not be transferred to the abutments. The 
width of the opening just short of this breaking point is called the maximum 
pressure arch or critical width, and it will vary with the depth of the 
overburden from the surface. Figure 98 shows this relationship as experi- 
enced in United Kingdom and West German coal mines. The distance from the 
ribs that the solid coal can support the overburden load depends upon the 
thickness of the coal, the strength of the coal, and the overburden strata. 



121 



■4J 


2000 


. 


/ 
/ 
/ 






w 
u 
< 

D 
U3 


1500 
1000 


... 


/ 
/ 
/ 

/ 
/ 
/ 






S 






/ 
/ 






Pm 


500 


- 


/ 






E-t 
On 
W 
Q 


n 


- 


/ 

t 1 










100 200 300 

CRITICAL WIDTH, 


400 

feet 


500 



FIGURE 98. - Critical width versus overburden (empirical) . 

Figure 99 is a representation of the stresses acting upon the roof strata 
above a mine opening. Outside the arch line, the stresses are predominantly 
compression stresses; inside the arch, tension stresses dominate. Because 
rocks ordinarily have several times as much strength in compression as in 
tension, normally only the roof strata within the arching limit shown will 
require support. 



1 ' / 


Compressive 




Ijn 


/ / /""" — 7T — "\ 4 \ \ 

L/ j l\\ \ W 


\ 


UTji 


'^/L/ Tensile \>r\ \ 


u\ 


' ' i (( 


r*~**^ , , — — """y \ \ 


\ \ i 1 


j Y f T v 




.Bshear Shear | ^r 





FIGURE 99. - Approximate distribution of roof 
stresses above an opening. 



122 



The Voussoir Arch 

When an entry is driven into coal, the strata above the opening form an 
arch. If the strata are not cemented together, or if the cementing material 
has been altered, each stratum within the arch line acts as an individual 
beam. The action of such a beam under these conditions is referred to as the 
Voussoir arch principle. 

Before a beam fails, it sags along its longitudinal axis. The maximum 
sag will be at or near the middle of the span, even though failure may occur 
at other locations (such as the ends) . When the immediate roof stratum or 
beam above an opening sags, cracks will open up in the underside, forming 
blocks like a row of dominoes. The upper corners of the blocks are in 
compression, which holds the roof together. However, if the blocks are 
relatively thin or if the end pressure is not great enough, the roof will 
buckle through. On the other hand, sufficiently thick blocks or sufficient 
pressure will allow the span to be increased. Apparently, the roof will be 
most stable if the top of the beam is hard rock, since soft rock would yield 
under the compressive stress and would allow buckling. Figure 100 illus- 
trates the Voussoir arch principle. 



Compression 



£1 



Tension 




The immediate roof sags, forming blocks 



I 



Thin blocks like dominoes lying flat are unstable 
in vertical loading 



• • « • • • • • 

• • • • • • 

• ••••• • • 



Thick blocks like dominoes on edge are more stable 
in vertical loading 

FIGURE 100. - The Voussoir arch principle. 

The domino arch is very sensitive; it does not take much additional down- 
ward pressure to buckle it, but only a small amount of support at the center 
makes the structure much more stable. That is why small wooden props can 
often do so much for roof control. Also, the sensitivity of the arch 
increases rapidly as it deflects — the more it sags or bends, the more easily 



123 



it can fall. This kind of structure should be supported in a mine as soon 
after raining as possible before it has a chance to start bending. 

Pillar Strength 

There is a relationship between the strength of a pillar and its minimum 
width. If height is variable, the relationship will be between strength and 
the height-to-width ratio. For a given height, a wide pillar is much 
stronger, per square inch, than a slender pillar; for a given width, a short 
pillar is much stronger than a tall one. This means that using the same 
dimensions for all pillars in a seam in which the thickness varies a great 
deal is inappropriate. Also, in a tall, slender pillar, many flaws are 
exposed and the pillar tends to fall apart, but in a very short pillar, the 
flaws are confined and the strength of the pillar is great. A pillar with 
its width equal to or less than the height has minimal strength. When this 
condition is reversed, a pillar may prove to be extremely strong. For 
example, when the width is around 10 times the height, the perimeter of the 
pillar may yield somewhat but the center is confined. Then, between the two 
extremes, there will be some width at which the pillar does not collapse but 
creeps slowly for years until eventually it fails. This behavior may occur 
when width is around twice the height. (See fig. 101.) The ratios are given 
only for comparative purposes and are not necessarily reflective of the 
behavior of coal pillars. Actual mine conditions and the type of ore will 
determine the actual ratios. For example, for a coal pillar to be infinitely 
strong, the width might need to be 10 times the height.!./ 

4/ Parker, J. Practical Rock Mechanics for Miners, Parts 1 through 7. Eng . 

and Min. J. , June-December 197 3 and January- February 1974. 




When height :width ratio is around 1:1, 

edges of pillar fail in shear, then 

tension cracks open up in center 





When pillar height :width ratio is around 1:2, 

gradual deterioration of the outer part of the pillar 

decreases the degree of confinement on the center, 

and increases the load on the remaining central portion 



Center of pil n ar is confined, 
hence very strong 



When pillar height :width ratio is around 1:4, 
roof deflects a little and exerts an inward force on the pillar 

FIGURE 101. - Pillar strength versus height-to-width ratio. 



124 





Equipment 

After completion of the dimensioning calculations based on principles of 
rock mechanicsf the engineer will have determined the minimum pillar dimen- 
sions required to support the overburden pressures of the area. Within this 
framework, the engineer must then select pillar dimensions that will allow 
efficient use of mining equipment on section. The following discussion 
describes the calculations to be made in the selection process. 

The working dimensions of the mining equipment must be considered when 
pillar dimensions are determined. An example of the required calculations is 
provided to illustrate the design process. In the example, the equipment 
dimensions for a continuous miner will be assumed. The two dimensions of the 
miner that determine optimum pillar size are cut width and miner reach. 
Miner reach is the distance from the machine controls to the front of the 
cutter head. These dimensions are as follows: 

Miner cut width: 11 feet 
Miner reach: 18 feet 

Other assumptions to be made in the example are maximum pillar dimensions 
resulting from either ventilation requirements (which are discussed later) or 
haulage length requirements dictated by the equipment used; the minimum pillar 
size determined by rock mechanics principles (as discussed previously) ; and 
standard roof bolt spacing. The assumed dimensions are — 

Maximum pillar dimension: 60 by 60 feet 
Minimum pillar dimension: 40 by 40 feet 
Roof bolt spacing: 4 feet 

The pillar extraction process to be used in the example is the split-and- 
fender process. The calculations can easily be adapted to other pillar 
extraction processes as well. 

The extraction of a pillar takes place by two types of cut. The first 
cut is the split cut. The split cut will be made to the depth of the miner 
reach from the last row of roof supports and will, in general, be the same 
width as the panel entries or crosscuts. In the example, the panel entries 
and crosscuts are assumed to be 18 feet wide. The roof bolting pattern of 
4-foot spacings will result in a row of roof bolts 3 feet from each rib. 

Since the roof bolts next to the ribs will be the last row of supports 
for the first split cut in the pillar, an initial split cut is 15 feet in 
depth (an 18-foot reach minus 3 feet to roof support) . As stated, this split 
cut will be the same width as the panel entries or crosscuts (that is, 18 
feet) . 

The placement of roof support in the first split cut on 4-foot centers 
will result in roof support to within 2 feet of the face. This means that 
the second split cut and all split cuts thereafter can be to a depth of 16 
feet (that is, an 18-foot reach minus 2 feet to roof support). 

The result of these split-cut dimensions is that split cuts will end at 
depths of 15 feet, 31 feet (15 plus 16), 47 feet (15 plus 16 plus 16), 63 



125 



feet, etc. Therefore, if the number of split cuts in a pillar is to come out 
exactly, the pillar length would ideally be 15, 31, 47, or 63 feet. However, 
as the next step in the example shows, setting the pillar length as an even 
number of cuts is not desirable. 

When the final split cut is completed and the miner breaks through to the 
gob, a double row of breaker posts is placed across the end of the split 
before proceeding with removal of the inby fender. The inby row of posts in 
the double row should be in line with the rib line at the breakthrough. This 
requirement places the other row of posts 4 feet outby the rib line and means 
that the last row of roof bolts (or the next row of posts) will be 8 feet 
outby the rib line. The result of this roof support requirement is that if 
the last split cut in a pillar is over 8 feet from roof support to rib line, 
roof bolting will be required. Since encountering a delay for bolting after 
the split is completed is undesirable, the last cut should be kept within the 
8-foot limit. Since the last row of roof bolts has already been determined 
to be 2 feet from the face before any given cut, the actual depth of cut for 
the last split cut will be only 6 feet. 

Combining these roof-bolting requirements with the full split-cut 
dimensions presented earlier will result in the following optimal pillar 
lengths: 21 feet (15 plus 6) , 37 feet (15 plus 16 plus 6) , 53 feet (15 plus 
16 plus 16 plus 6) , 69 feet, etc. The first and second of these must be 
eliminated because they result in pillars smaller than the minimum dimension 
needed for roof support. The requirements of haulage and ventilation make 
the use of pillars larger than 60 feet undesirable; therefore, the optimum 
pillar length for the equipment and other conditions given will be 53 feet. 

Now that the pillar length has been determined, the pillar width can be 
calculated. The primary factor in determining optimum pillar width is the 
dimensions of the second type of cut, the fender cut. The fender cut is a 
single-pass, angled cut into the fenders that are left after splitting the 
pillar. This cut should break through the fender into the gob to aid ven- 
tilation and roof control. 

The dimensions of this cut will be the cut width (11 feet) and the miner 
reach (18 feet) . However, since this cut is taken on an angle, these dimen- 
sions must be adjusted to arrive at a desirable fender width. For purposes 
of this example, the cut will be taken at an angle of 60°. Figure 102 
shows the miner reach and its equivalent fender width. 

This figure shows that a fender 12.6 feet wide can just be broken through 
by a miner with an 18-foot reach at a 60 angle. In order to be some- 
what on the safe side for breakthrough, a fender over 12 feet in width is 
probably not desirable. This fender width, when combined with the split 
width of 18 feet, results in a pillar width of 42 feet (18 feet plus two 
12-foot fenders) . Since 42 feet is within the dimension range determined by 
rock mechanics and haulage and ventilation requirements, this pillar width is 
acceptable. Thus, in this example, the optimum pillar dimensions for equip- 
ment efficiency, within the limitations of rock mechanics and other consid- 
erations, will be 42 feet wide by 53 feet long. 



126 




3'-» —12.6'-* 



■Miner reach 



Fender width=12.6 feet 
(15.6 feet miner reach 
minus 3 feet to roof 
support) 



f 




/ 


't 


Face 




V # 



FIGURE 102. - Optimum fender width. 



Ventilation 



Ventilation requirements rarely affect pillar dimensioning directly. 
However, they do affect the size of entries and thus may indirectly affect 
pillar size. Ventilation requirements may also determine the number of 
entries needed in a section. This factor, in combination with equipment 
limitations, can affect panel width and thus pillar dimensions. 

Historical Practices 

Unfortunately, history is frequently the sole determining factor in 
establishing pillar size. There are many areas of the country where a 
particular pillar dimension is used simply because everyone in the area has 
always used that size. There are two points of discussion concerning this 
tendency. 

One point frequently made in favor of the historical approach is, if a 
particular size has been working under the conditions of a particular area, 
there is no apparent reason to change it. This is a powerful argument, and 
the plans that are working in a particular area should be given definite 
consideration in the process of establishing the dimensions of developing 
panels. However, the second point is that the plans that have been used in 
an area over many years may have been developed under entirely different 
conditions. The mining plan that may have been optimal under the roof and 
equipment conditions of 30 years ago may not be at all efficient today. 
Therefore, historical practices should be a part of the decisionmaking 
process but not the sole determining factor. 

Bleeder Systems 

One of the requirements of the 1969 Coal Mine Health and Safety Act that 
has strongly impacted the practice of retreat mining is the requirement for 



127 



bleeder entries or systems. In virtually all retreat-mining operations, a 
bleeder system will be required. Bleeders are entries that encircle a mined 
out area. The purpose of these entries is to bleed methane and other explo- 
sive gases from a gob area and move them into the main return airways. The 
principle behind bleeders is that air enters the mined out area from the 
intake air side, filters through the gob area, and carries methane and other 
explosive gases into the bleeder entries and finally into the main return 
airway and out of the mine. Bleeder entries should be maintained free of 
excessive water accumulations and roof falls to be effective. The top of 
bleeder entries should be well-supported and they should be accessible for 
periodic inspection. Only in those areas where partial oxidation of exposed 
areas could result in spontaneous combustion will the practice of sealing 
caved areas be substituted for bleeders. 

There are three areas of design that result in differences between the 
various bleeder systems: 

1. The method by which air is conducted through the panel. 

2. The connections, or lack thereof, between panels. 

3. The method by which return air is collected from groups of panels and 
routed to main return entries. 

Each of these design areas and their relationships with one another will be 
discussed in the material that follows. 

Panel Bleeding 

There are primarily two alternatives available for the bleeding of in- 
dividual panels — total extraction and incomplete extraction. Total extrac- 
tion of a production panel involves the second mining of all possible pillars 
in the panel. Air must be able to flow through the gob that remains after 
the extraction is completed. In many cases, after extraction is completed, 
the gob falls tightly, compacts itself, or even cements itself together in 
such a manner that it will not conduct air. The practice of bleeding 
requires that a differential air pressure be established that will cause air 
to flow from the gob into the bleeder returns. If the gob is packed so 
tightly that airflow is not possible, the total extraction of individual 
panels will not be possible. 

The alternative to total panel extraction is incomplete panel extrac- 
tion, which is the practice of systematically leaving a row of pillars to 
provide an air passage through the panel. Incomplete panel extraction should 
not be confused with partial pillar extraction, which is the practice of 
extracting individual pillars in such a manner that caving of the main roof 
is not achieved. 

Figure 103 compares panels extracted using the two different methods. 
The panel on the left has been totally extracted, with the return air perco- 
lating through the length of the gob into the return entries. The panel on 
the right has beeen incompletely extracted, leaving the pillar between 
entries 1 and 2. This pillar protects entry 1 from closure. This entry will 



128 



be connected to the return and will serve as a source of constant negative 
air pressure to bleed the panel. 

A dense, consolidated, blocky immediate roof would tend to form a loose, 
porous gob that could be bled successfully with total extraction. At the 
other end of the scale, an unconsolidated, laminated immediate roof would 
tend to form a dense, compacted, impermeable gob that would require incom- 
plete panel extraction for successful bleeding. 



O DPDQ.0 a 
.Q- : DQQQ'D D 
O O O G O O O 

;D : .D':GiC3 GO D 

■oo o noon 
q.'.d a a a. a a 
QflD.-DQDD 

'l 2 3 4 5 6 7 £ 
Total Extraction 



qip o oaao 

□ q a a g oo 

D'D"Q:QDDQ 

d;£3 a a. o a q 

□ a a o a a a 
a o q n d d q 

a o,Q o a d a 



1 2 



7 8 



Incomplete Extraction 



FIGURE 103. - Panel bleeding. 



Panel Interconnection 



As with panel bleeding, there are two alternatives for panel intercon- 
nection — interconnected and independent. In interconnected panel design, 
there is no barrier pillar between panels, and the gob from one panel is 
contiguous and generally indistinguishable from the gob of other panels. 
Using this system, the entire interconnected gob is bled as a unit with the 
return removing contaminated air from the group. When using independent 
panel design, a barrier pillar is maintained between panels and each panel is 
bled as an individual unit. The bleeder returns receive air from each panel 
rather than from groups of panels. Figure 104 shows interconnected and inde- 
pendent panels. 



129 



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In a practical sense, it is frequently desirable to maintain independent 
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retreated. This provides needed ventilation control while on advance and yet 
has the simplicity of interconnected panel bleeding when the panels are 
completed. The pane] design discussed in the "Full Panel Extracted on 
Retreat" section of cnapter 5 is such a system. 

Because of the larger area subject to common bleeding, the interconnected 
panel bleeder design requires the presence of a relatively open gob. A 
closed gob that accepts airflow with difficulty will necessitate the use of 
independent panel bleeding. The desire to provide independent control and 
monitoring of individual panel bleeding is also a strong factor in favor of 
independent panel bleeding. The major advantages of the interconnected panel 
bleeder system are its simplicity and higher rate of recovery (no losses in 
barrier pillars between panels) . 

Panel Connection to Returns 

The third area of bleeder design is the connection of the panel bleeders 
to the main returns. Design options are to provide a separate bleeder entry 
or to use existing panel development. These are illustrated in figure 105. 



130 



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Use of Panel Portion as Bleeder 



FIGURE 105. - Panel connection to bleeders. 

A separate bleeder entry has many advantages in terms of control, dilu- 
tion, and bleeder design, but it results in great sacrifices in terms of 
reserve recovery, cost, and possibly productivity. In the practice of pro- 
viding a separate bleeder entry, two sets of submains will be driven for each 
set of production panels. The panels will be developed from one set, and the 
bleeder connection will be made to the other set when panel development is 
completed. The first set of submains will be used for haulage, supply, and 
primary ventilation. The second set of submains will be used as bleeder 
returns only. If necessary for gas dilution, intake air can be run in part 
of the bleeder submains and mixed with the return air as it enters the sub- 
main from the panels. This practice is expensive and should not be done if 
other solutions to the gas concentration problem can be found. 

The use of existing panel development entries (or crosscuts) is a more 
efficient and easier process if conditions permit. In this system, the 
panels are developed to their extremities, and the extreme inby rows of 
pillars are allowed to remain. Connections are made between the standing 
sections of the various panels, and these connected sections are used as the 
bleeder return. Some control of individual panel ventilation is sacrificed in 
using this system. In addition, fewer panels can generally be ventilated 
using this system than with a separate bleeder submain. Even with these 
sacrifices in control and panel grouping, however, the use of this system if 
the panels can be successfully bled is generally desirable. One of the 
conditions that might necessitate using a separate submain system is a 
condition of extremely high gas emission. In this case, blocking out entire 
production panel sections prior to mining to allow some gas bleedoff may be 
desirable. This is not possible with the use of existing panel entries for 
bleeder returns. 



131 



These alternatives indicate that there are eight basic bleeder system 
designs. Since some of the design alternatives are beneficial under similar 
conditions , there likely will be a tendency to use them together. For 
example, the conditions that favor total extraction also favor intercon- 
nection/ and therefore there is an expectation that the two would normally be 
used together. 

Retreat Mining and Bumps 

Under certain conditions, coal can be subject to sudden releases of 
stored pressure. These releases, known as bumps or bursts, frequently 
resemble explosions and can involve the expelling of significant amounts of 
coal. Bumps can easily result in damage to nearby equipment and injury or 
even death to personnel. Where these conditions exist, retreat mining 
becomes a delicate operation that must be performed with caution and pre- 
cision. If certain precautions are taken, however, there is no reason that 
retreat mining cannot be conducted under bump-prone conditions. The follow- 
ing discussion will describe the conditions under which bumps are likely to 
occur and then will present the techniques for successful retreat mining in 
bump-prone areas. 

Bump Conditions 

The conditions that result in bumps can be divided into geological con- 
ditions and physical conditions. Geologically, the primary prerequisites are 
a hard, unyielding roof and floor. When mining takes place in a seam between 
a hard roof and a floor, the energy generated by the inevitable (if minute) 
roof movements cannot dissipate itself into the lower strata; therefore, it 
is stored. Over time, a significant amount of energy can build up in the 
coal pillars. If this stored energy is slight, bumping will not occur. 
Because of this, bumping rarely occurs in areas where the overburden is less 
than 500 feet but becomes a common problem if the overburden is 1,000 feet or 
more. 

Another geologic condition involves the coal type. The areas that have 
the severest problems with bumps generally have coals that are of a spongy, 
energy-absorbing nature. These coals store large amounts of energy until 
they reach their yield points and then fail suddenly and often catastrophi- 
cally, releasing this energy in one burst. 

In summary, there are three geologic conditions that contribute to bumps: 

1. Hard roof and floor 

2. High overburden pressures (1,000 feet or more) 

3. Energy-absorbing coal 

In addition to these geologic conditions, certain physical conditions con- 
tribute to the occurrence of bumps. The two major physical contributions 
are — 

1. Nonuniform size pillars, particularly a single large pillar in an area 
of smaller pillars. 

2. Hanging roof falls. 



132 



In the former case, the smaller pillars are likely to yield for stress 
relief. Most of the load is then transferred to the large pillar. If the 
load is too great and too much energy is stored in the pillar, bumping may 
occur. In the latter case, the load from a hanging roof fall will be trans- 
ferred to the surrounding pillars. Again, if the load is too great upon 
these pillars and other bumping conditions prevail, they may be subject to 
bursts. 

Mining Practices 

Although retreat mining under bump conditions is not an exact science, a 
number of practices have been found to be successful through trial-and-error 
testing. These techniques are largely based on the following: 

1. Bumps occur in pillars that are in a certain "critical" size range. 
Pillars larger than the critical size appear to be incapable of 
storing sufficient energy to bump. Pillars smaller than the critical 
range have already yielded and cannot store energy. 

2. Bumps generally occur along the pillar line where pressures are 
highest. 

3. Bumps usually occur on the long side of a pillar. This fact is 
important because mining performed on the short side of a pillar is 
relatively safe. Figure 106 is helpful in illustrating this point. 
The pillar in this figure is in the process of being split. The most 
likely locations for bumps during this splitting process are marked at 
A and B. These two locations are on the long side of the pillar, 
approximately opposite the working face. Obviously, personnel should 
avoid the areas around points A and B. 




FIGURE 106. - Pillar locations susceptible to bumping during mining, 



133 



Some of the practices that are used to control bumping are described 
below: 

1. Uniform size blocks are mined, particularly in sections that will be 
undergoing retreat mining at some future date. Uniform blocks tend to 
eliminate load concentrations that can be the site of bump problems. 

2. When mining on retreat, rooms are developed on very short centers to 
the left or right of the main panel, leaving relatively small blocks 
of coal that can be taken as fenders (the outside-lifts method) . The 
solid coal into which the original rooms are cut is too large to be 
sufficiently loaded to cause bump problems. The small pillars that 
remain after the rooms on narrow centers are cut are sufficiently 
small that yielding has occurred, and bumps will not occur in them. 
The difficulty in this mining plan is primarily in the mining of the 
chain pillars in the entry panel itself. There are other techniques 
used for mining these pillars. 

3. To mine chain pillars and other developmental pillars, size-reducing 
cuts, known as bump cuts, are made relatively far ahead of the active 
pillar line. In executing this method, the section crew will make 
outside cuts or even sometimes full splits into chain pillars or other 
developmental pillars two or three crosscuts in advance of the 
retreating pillar line. The difficulty with this method is that, when 
making size reducing cuts in the pillars, the crew must pass the 
pillar through the critical size during which it is subject to bumps. 

4. Any cut or significant reduction in size of a pillar is done rapidly 
before the overburden pressures have sufficient time to rest on a 
pillar and allow it to absorb sufficient loading to bump. This prin- 
ciple can be used when performing the previously described method. 

In this case, it is essential that the bump cuts or size reducing cuts 
be made in a rapid and expeditious manner so that they can be com- 
pleted and removed from the pillar before the load has had a chance to 
settle into the area. 

5. Cuts are made in the small side of rectangular blocks being split or 
reduced. A crew should be cautious of the area adjacent to the face 
along the rib of the outside of the long side of the block because it 
is prone to bump activity. 



134 



Chapter 7. SECTION OPERATIONS 

Mining Operations 

Whether using conventional or continuous mining equipment, the proper 
execution of mining operations is essential to obtain acceptable productivity 
levels. This is particularly important in retreat mining where the failure 
to follow basic principles of mining can not only cause serious delays but 
also increase exposure to hazardous conditions and lead to the loss of valu- 
able resources. There are four specific areas in which the section foreman 
can make improvements in mining operations: the preparations for mining in a 
place; the mining of pockets, splits, fenders, wings, and pushouts; the com- 
pletion of mining in a place; and the execution of the place change. Each of 
these areas is discussed in the section below. 

Place Preparation 

Before beginning the mining operation, the foreman must take steps to 
ensure that the working place is safe. Roof and rib falls are the leading 
causes of fatal accidents in the coal industry. This is of particular 
significance in retreat mining where changes in roof pressures can create 
rapidly deteriorating conditions. The nature of retreat mining dictates that 
conditions will have deteriorated since the last cut was taken in any given 
place. Therefore, it is important to take the time to carefully test the 
roof and scale down any loose material prior to the beginning of mining. 
Ribs, too, must not be overlooked. As the pillar takes pressure, sloughing 
of the ribs will create additional hazards. All corners and notches should 
be examined to ensure that they are adequately supported. 

On occasion, debris carelessly discarded has been picked up by the 
miner's cutting head and flung at workers in the area. This is even more 
likely to occur in retreat mining because of the quantities of cap blocks, 
wedges, and other pieces of timber discarded as the posts are set. There- 
fore, debris along the roadway or at the face should always be cleared away. 

An efficiently operating section is an orderly section. Posts to be set 
should not be carelessly tossed in a pile at the point of the pillar split. 
Rather, they should be stacked neatly and as close to the point of use as 
possible. Saws and other tools should be left in a convenient place, easily 
seen, but out of the way. Curtains or air ducting should direct the air 
current in the proper course. A methane concentration check should be made. 

Mining in a Place 

The mining operations differ slightly when mining pockets or splits, 
fenders or wings, and pushout stumps. Before mining the pocket or split, the 
foreman must apply basic survey techniques and must take the time to care- 
fully measure the point at which the cut is to be initiated. Whether using 
conventional equipment or a continuous miner, failure to properly deter- 
mine the point at which to initiate the cut can lead to improper dimensions 
of the fenders or wings. This could cause pillar failure and subsequent 
injury or create a situation where the crew is likely to go beyond supported 
roof to obtain complete extraction. Site lines should be made on the top, 



135 



and site rods should be hung to assist the continuous miner operator in 
maintaining direction. 

Additional roof bolting prior to initiating the pocket or split is recom- 
mended. By installing roof bolts against the rib, as much as 20 percent more 
coal can be extracted in a given cut. 

In making the split with a continuous miner, the box cut on the right 
should be advanced 10 feet. At this point, the continuous miner should be 
pulled back and the curtain advanced to the face. The cut on the left then 
can be advanced a full cut (up to 20 feet) because the curtain is now still 
within 10 feet of the face. Last, the final cut on the right hand side can 
be completed. 

Once the pocket or split is completed, the next step is to extract the 
fender or wing. These operations are the more productive part of retreat 
mining since no roof bolting is required, but they should be performed with 
extreme caution due to the hazards involved. The roof control plan is a 
guide for the extraction of fenders or wings. It reflects the experiences of 
the mining company and of the mines in the immediate area. The experience of 
the crew is also important in determining exactly how much coal can be 
extracted. 

After turn posts are set in preparation for the extraction of the fender 
or wing, the continuous miner should be turned between 30° and 45° to 
extract the fender. These cuts are generally taken to the right, keeping the 
miner operator against solid coal. However, in the pocket-and-wing methods, 
some cuts must be taken to the left. In these instances, more coal can be 
extracted while under support because the reach of the continuous miner while 
turning to the left is significantly longer. Discretion should be used, 
however, since the operator is no longer against solid coal. 

When the splits are being roof bolted, the subsequent mining of the 
fenders and wings should be considered. Bolting should be close to the inby 
fenders and wings; this will provide a greater margin of error to the 
equipment operator to prevent mining in unsupported areas. 

As the mining of the fender or wing progresses, the miner operator's 
helper should be positioned to watch both roof and rib conditions and 
activity in the gob. Small stumps of coal can be left to act as indicators 
as the remaining coal is removed. 

The mining of pushout stumps is the most hazardous stage of pillar ex- 
traction and should only take place with the foreman present. Care should 
should be taken to ensure careful adherence to the roof support plan. Spot 
bolting close to the rib should take place prior to the extraction of the 
fender or wing. 

A double row of breaker posts should be installed on both sides of the 
roadway leading to the final stump. The roadway should not exceed 14 feet in 
width. Only one roadway should be maintained to the final pushout. 

The mining of final stumps must be done with a minimum of delays. Once 
mining has commenced, it should not cease until the stump is extracted or 



136 



abandoned, since roof deterioration is rapid. The proper method of extrac- 
tion is to hit the stump head on. Attempting to narrow the stump from the 
side is a more hazardous method of mining. As much coal as can be safely 
mined should be taken. Under no circumstances should miners go beyond 
supported roof. 

Completion of Mining 

When mining of a pocket or split is completed, the equipment should be 
pulled back and a danger sign hung pending the installation of roof support. 
After the area is roof-bolted, the place should be thoroughly rock-dusted. 
If a scoop is available, it is also worthwhile to thoroughly clean all loose 
coal from the pocket or split. This coal should be placed at the face so 
that it can be loaded out before the initiation of the next cut. This 
cleanup is part of good housekeeping and will pay dividends as the remainder 
of the pillar is extracted. 

Place Changes 

The proper execution of the place change is one of the most important 
components of a high-productivity section. A place change from one block to 
another can normally be executed in under 10 minutes. By utilizing the 
techniques shown earlier in this manual, check curtain moves and shuttle car 
anchor point moves are kept to a minimum; the movement of the continuous 
miner should be the only time-consuming operation. The equipment cables 
should be fastened to the equipment so that the tramming of the equipment 
pulls the cable in the appropriate direction. Attention must be given to the 
location of the cables in the entries to minimize the amount of time spent in 
hanging cables. The movement of a piece of equipment is a team operation and 
requires four or more people. The section foreman must ensure that adequate 
labor is available and that individuals know their proper assignments. Non- 
critical operations should be stopped temporarily and labor reallocated to 
assist in the move. Remember, time lost in moving from one working place to 
another can never be regained, and production and productivity will suffer. 

Many mining crews move the equipment quickly only to encounter delays for 
other reasons once the equipment is at the new face. The foreman should 
ensure that place preparation is completed prior to the initiation of the 
place change. All ventilation curtains should be hung, timbers and posts 
should be installed, and sights should be set. Once the continuous miner 
trams to the face, the crew will have only to make the necessary safety 
checks. Then mining can commence. 

Conventional mining requirements are not vastly different. Except for 
the complexities created by the additional equipment, the same principles 
apply to conventional mining as were discussed for continuous miners. 
Usually, the movement of one particular piece of equipment is the key to the 
whole system. The section foreman should ensure that this particular opera- 
tion is adequately staffed so that it does not create delays. Cable handling 
is perhaps more difficult due to the possibility of tangling cables. A set 
procedure must be followed in moving equipment to avoid tangling cables. 



137 



Roof Support Operations 

Roof control devices such as timbers and posts are intended to support 
the immediate roof — the rock that lies directly above the coal seam. Coal 
pillars provide support for the main roof. In advance mining, the intent is 
to keep the roof in a stable condition, since any deterioration in the roof 
is irreversible; it is best to prevent the roof from moving at all. In 
retreat mining, the strategy is somewhat different, because some yield is 
desirable. Pillars should begin to take weight. As a pillar is extracted, 
more and more weight is held up by a smaller part of the pillar. 

After extraction is completed, a quick fall is desired, so too much roof 
support in terms of coal left in stumps, roof bolting, and timbers and cribs 
could be detrimental to the efficient operation of the section. Therefore, 
minimal roof support should be installed provided that sufficient allowance 
is made for variations in conditions. 

Roof Bolting 

Roof bolting is required in all areas inside the pillar block where per- 
sonnel will be actively working. Pockets or splits are supported to within 8 
to 10 feet of the end. The remaining areas need not be bolted, but breaker 
posts should be set to isolate them so that the remainder of the coal in the 
fenders may be extracted from a safe position. 

Roof bolts should be inserted as close to the face as possible. If, 
after installing roof support, 2 to 3 feet remain between the last row of 
bolts and the face, one more row of bolts tight against the face will improve 
productivity since it will allow the continuous miner to advance deeper into 
the coal. Similarly, since coal will eventually be extracted on the gob side 
of the split, the installation of roof support tight against the rib on that 
side is also advantageous. Bolts should be inserted close against the rib 
also at all points where pockets or splits are to be driven. The roof 
bolting in these three areas should occur prior to commencement of mining. 

The area where the final pushout stump is to be recovered should not be 
overlooked. Again, roof bolts should be inserted as close to the rib as 
possible and in the early stages of pillar extraction; installing any addi- 
tional roof support safely will be difficult once the pushout is ready to be 
recovered. 

All areas where roof bolting is not necessary should be posted. Once the 
pocket or split is driven to within 8 feet of the end of the block, the 
remaining coal can be extracted safely without additional roof bolts, but 
posts must be installed to provide necessary support prior to mining. 

Timbering 

Timbers are used in abundance in retreat mining as breaker posts, turn 
posts, roadway posts, and cribs. The posts themselves do not differ at all 
in construction; however, the theory of application is different for each 
use, and each merits separate discussion. 



138 



Breaker posts are set at each entry that is exposed to the mined-out 
area. Primarily, breaker posts act as a continuation of the pillar line, 
filling in between one pillar block and another so that the roof breaks along 
a straight line. Without breaker posts, a roof fall may ride between pillar 
blocks into entries. Breaker posts also serve as warning devices to indicate 
the entrance to a dangerous area. Breaker posts are set commonly in double 
rows, two posts set close together on 4-foot centers. In some areas where 
conditions are extremely hazardous, cribs may be set in lieu of breaker 
posts. 

Turn posts are used to provide protection for the equipment operators. 
They should be installed anytime cuts are taken in fenders or wings and at 
the entrance to all splits or pockets. Turn posts alone, however, do not 
adequately support the roof. Therefore, they should be viewed as indicators 
of movement in the roof, not as support. 

Roadway posts are installed along the roadway prior to the extraction of 
pillars. They are intended to decrease the width of the roadway to a maximum 
of 16 feet. (A common assumption is that the maximum safe entry width is 20 
feet.) As pillars are extracted, the perimeter of the pillar will deterio- 
rate to a point at which the pillar is no longer effective in holding the 
roof. The installation of roadway posts is an important step to make up for 
decreases in the effective load-carrying capability of the pillar. 

Cribs are used in place of breaker posts in many areas where conditions 
are hazardous. Typical locations are inby the split in rooms or crosscuts or 
in place of the breaker posts in preparation for the final pushout stumps. 
Cribs, being more expensive, are commonly recovered where possible. 

Section Ventilation 

Each working section is ventilated with a minimum of 9,000 cubic feet per 
minute of air at the last open crosscut. This air must not contain less than 
19.5 percent of oxygen and not more than 0.5 percent of carbon dioxide. At 
least 3,000 cubic feet per minute must reach each working face where coal is 
being mined. 

While a panel is being developed, all air going to the section (except 
air used to ventilate the haulage entry) is directed to the face by means of 
curtains across entries, line curtains, or auxiliary fans. This air is then 
directed to the section return, to the main return, and then to the outside. 
The air used to ventilate the haulage entry is curtained off outby the load- 
ing point and is vented directly into the section return. While rooms are 
driven and pillars extracted, air going to the section is usually split at 
the active pillar, with some going to the section return and the remainder 
flowing across the gob to the bleeder system. 

Curtains 
Check Curtains 

Check curtains stop the airflow and direct it in a different direction. 
They also serve as temporary regulators. Burlap or plastic curtains are 



139 



placed across entries/ or crosscuts, to help direct the flow of air to the 
face for ventilation purposes or prevent air from flowing into the gob. 
Special care must be taken when equipment is moved through check curtains to 
prevent tearing the curtains down and interrupting the ventilating air 
current. If a curtain is accidentally torn down, it should be replaced 
immediately. 

Fly Curtains 

Fly curtains serve the same purpose as check curtains but are installed 
in individual panels so that shuttle cars or other equipment can drive 
through without pulling the curtain down. To install fly curtains, boards 
are bolted across the top of the entry or crosscut and the curtain panel is 
securely nailed to the board. 

Face Curtains 

A face curtain is hung to direct air into a face that has advanced beyond 
the last open crosscut. These, curtains are used primarily to keep the face 
area free of gas accumulations. Face curtains must be maintained within 10 
feet of active working faces. 

Auxiliary Fans 

Blower Fans 

Blower fans must be permissible and are to be maintained in this condi- 
tion. This type of fan is installed in intake air. The volume of the intake 
air should be 2-1/2 times the manufacturer's rated capacity of the fan. The 
fan should be positioned at least 16 feet outby the nearest corner of the 
place to be ventilated and on the intake air side. The tubing must be 
capable of delivering at least 3,000 cubic feet per minute of air to each 
face. A blower fan can ventilate two faces simultaneously by using a Y-joint 
in the tubing. 

Rock dust or a suitable fire extinguisher must be kept on the intake air 
side of the blower fan. A rubber mat should be kept under the blower fan so 
a person can stand on it while turning the blower on and off and be protected 
against electrical shock. The cable from the transformer to the fan must be 
hung from the mine roof and must not be allowed to touch the roof or rib. 

The fan and tubing should be checked by the section foreman at the 
beginning of each shift for correct operation. To check for the proper 
volume of air passing over the fan, air readings should be taken every 2 
hours during the shift and recorded in a record book maintained on the blower 
fan. 

Exhaust Fans 

Using an exhaust fan safely and effectively can greatly cut down on the 
amount of dust in the mine atmosphere. This not only reduces the amount of 
respirable dust but increases visibility and cuts down on explosive float 
dust in the work area. It also helps remove methane gas from the face area 
into the return airway. 



140 



Exhaust fans pull the dust and gas from the working face area through 
plastic or fiberglass tubing. The dust is then discharged into the return 
air entry. Care must be taken in hanging the tubing so that as few leaks as 
possible are in the tubing. The tubing should be maintained no farther than 
10 feet from the working face at all times. The tubing should always be hung 
on the left side of the continuous miner for maximum effectiveness. 

Some considerations when using exhaust fans include — 

1. Positioning the exhaust fan where it will discharge into the return 
air. 

2. Hanging all of the exhaust fan power cable from the roof and placing 
a rubber mat at the control switch. 

3. Hanging the exhaust tubing on the left side of the continuous miner 
no more than 10 feet away from the working face area. 

Panel Stopping 

Panel stoppings are installed to direct air to the active areas of a 
working section. Stoppings are placed in crosscuts throughout the length of 
the panel to separate intake air, return air, and the haulageway. 

Stoppings are of concrete block construction (solid or hollow blocks) . 
A stopping can be constructed with mortared joints (wet) or can be built by 
stacking concrete blocks and later spraying with a sealing coating or cover- 
ing with mortar on the pressure side. 

In designing stoppings, the construction time gained by using dry 
construction must be weighed against losses in stopping strength and 
increased leakage. Stoppings must be maintained to separate intake and 
return airways to within two crosscuts of the face or active pillar line. 

Planning for and Moving Supplies on Section 

To ensure that needed supplies are at the proper location at the proper 
time, two conditions must be met. First, information concerning the supply 
need must be available and properly communicated. Second, the supplies 
themselves must be handled in a manner that will place them in the needed 
location at the right time. An information system and a material-handling 
procedure will be discussed in the material that follows. 



Information System 



Overview 



The information system related to supply handling includes many areas 
that are not directly related to the section's operation or under the control 
of the section foreman. Some of these areas include the material replenish- 
ment activity, yard storage locations, and vendor delivery schedules. This 
discussion will be limited to the information required directly to accomplish 
the loading and scheduling of cars for section usage. 



141 



The most important information related to planning for and moving sup- 
plies on section is what supplies are needed, where, and when. This infor- 
mation is properly determined at the section level and transmitted to the 
supply yard for proper response. 

Information Flow 

Supply requirements for operations at the face and support activities are 
determined by the section foreman. A forecast system based on past experi- 
ence or a demand system based on the day's needs can be used to provide 
supplies. With the former, considerable variance from a forecast is normal 
due to unexpected equipment downtime and geological variability. Information 
on the exceptions to forecasted requirements or a full day's requirements 
must be communicated from the section to the supply yard. 

A typical information flow activity would begin with the section foreman, 
who determines requirements based on the rate of mining, geological charac- 
teristics encountered, and other factors. Requirements are communicated to a 
supply foreman, who lists the requirements by shift and section. No approval 
should be required for routine production supplies. The list is forwarded to 
supply-handling supervisors, who, in turn, direct the loading of goods onto 
supply cars and their delivery. To close the information loop, it is sug- 
gested that the section foreman routinely acknowledge receipt of the requested 
supplies rather than respond on an exception basis when he observes shortages. 
Special or emergency requests should go directly to the supply yard to avoid 
unnecessary delay. 

Material Handling 
Overview 

Retreat mining supply requirements are different from those of advance 
mining, not only in terms of quantity and type (for example, a greater number 
of posts are consumed per ton of coal produced) but also because considerable 
losses result from supplies being left in the gob area and the trip distance 
is continually shortened rather than lengthened. A system using a standard 
supply load based on forecast requirements appears to offer the best answer 
to section supply handling problems. For this system, supply usage is 
forecast, and each day, a car containing the maximum number of supplies for a 
day is pulled to the section. The car from the previous day is recovered, 
with unused supplies remaining on the car. These are taken outside and 
returned to stores. The primary advantage of the standard car supply system 
is the elimination of double handling, reduction in track-side clutter, and a 
tendency to reduce supply waste. Some disadvantages of this system are the 
need for more cars, need for parking space on the section, and extra car 
shifting. 

Supply Materials 

Generally, there are four broad categories of supplies required on 
section: 



142 



Production Items . — These items are associated with the face operation and 
are generally considered to be expendable. Examples are posts, wedges, crib 
blocks, roof bolts and plates, rock dust, and brattice. 

Support Items . — These items are all other nonequipment goods used on 
section in support of production. Examples are rail, ties, trolley wire, 
trolley feeder cable, pipe, and hand tools such as shovels, saws, and 
hammers. Some production items fall into this category. 

Equipment Maintenance Items . — These items are generally broken into two 
categories, expendable and nonexpendable. Examples of expendable items are 
miner bits, roof bolter bits, and other cutting tools that may be used on 
section. Examples of nonexpendable items are all spare parts, cables, pipe 
fittings, nuts and bolts, hydraulic and air hoses, oxygen, acetylene, and 
tools. 

Lubricants . — These items include all lubricating oils, greases, and 
hydraulic oils used to maintain equipment. 

Material Flow 

In a standard car supply system, the typical material flow cycle begins 
with a forecast requirement for each section. One standard car, for example, 
would always contain a specific quantity of posts and a specific quantity of 
wedges. Another would always be loaded with a specific quantity of crib 
blocks, roof bolts, and plates, while another car might contain a given 
quantity of rock dust bags. Another car would contain equipment maintenance 
items, parts, and brattice. A separate car would be used for lubricants. 
These cars would be loaded in the supply yard and arranged by section within 
the supply trip train. The arrangements of these cars within the section 
should always place the timber cars so that they end up close to their point 
of transfer. Arrangement of the various sections* supply cars within the 
trip is based upon the desired sequence of materials to be dropped off. 

When the trip arrives at the specific section, the cars are parked as 
close to the face as is appropriate for that particular section. During the 
day, supplies are removed from the cars as they are used. By doing this 
properly, double handling is virtually eliminated. Typically, supplies are 
transferred to scoops or shuttle cars for movement to the immediate vicinity 
of their ultimate usage. This supply handling should be done when the miner 
is nonproductive, such as during place changes or servicing periods. Unused 
supplies remain on the cars and are returned to the supply yard. The unused 
supplies will become the base for the next set of standard cars. Recovered 
supply items such as rail or trolley wire are loaded onto the cars for return 
to supply storage. These recovered items are prepared for loading as they 
are recovered but are not loaded until immediately prior to removing the 
empty cars to the supply yard. Rails (except very short sections) require 
special cars that would be used for supplies on a scheduled periodic basis 
based on the rate of retreat. 

Whether it is better to remove the empties before delivering the loaded 
cars is a matter for careful consideration. Some factors affecting this 
decision are as follows: 



143 



1. Time for removing empties and delivering fulls versus shifting cars 
and/or rearranging the supply trip at the section. 

2. Availability of cars. 

3. Sufficient parking space on the section. 

4. Traffic conditions. 

Other systems of supply handling exist, but all suffer from decided 
disadvantages, particularly double handling. The standard car supply system 
concept keeps the supplies mobile, to be advanced or retreated as the section 
moves. This capability can greatly improve supply handling at a minimal 
cost. 

Forecasting Supplies 

Forecasting is simple, based mostly on common sense. The following 
hypothetical example is given for descriptive purposes. It should be used as 
a learning tool and not for direct quantitative application. 



Assumed conditions 

High-grade coal 

Low methane emission 

Belt haulage 

Rail supply system 

Three-shift operation 

6-foot seam 

315 tons per shift production 

18-foot-wide entries and splits 

36-foot-square pillars 

One pillar per shift 

32 roof bolts per pillar split 

93 posts per pillar 

Nine bags of rock dust per pillar (one bag per 4 feet of split) 

The split and fender pillar extraction process is assumed, using the plan 
given in figure 107. 

Estimating a day's requirements 











Minimum quantity 


Item 




Calculation 


per day 


Coal production 


(tons) 


315 x 3 




975 tons 


Pillars (blocks) 




1x3 




3 pillar blocks 


Roof bolts 




32 x 3 




96 bolts 


Bolt plates 




32 x 3 




96 plates 


Posts 




93 x 1 x 3 




277 posts 


Wedges 




93 x 2 x 1 


x 3 


54 4 wedges 


Rock dust 




9x1x3 




27 bags 



144 



r- 


- 




,' c 








:::: M :: 

y' . t: 


■ -UN 

" /I 


^ 






<: : '..'•' .".* 


/ 




. . • • . ...... 


* 






_^ 


TAZJ 



FIGURE 107. - Split-and-f ender extraction plan for supply forecasting. 

The additive shortage factor related to the items listed above should be 
based on the individual item rather than on the group as a whole. As a 
starting point, one might add 10 percent to 15 percent per item. This number 
could then be rounded off to the nearest full quantity unit load as purchased 
or stored. Maintaining extra supplies to allow for peak production is desir- 
able, since without the proper number of supplies, production is curtailed. 
Although goods not used will automatically be recycled, it is best not to 
recycle too many items because this causes problems in loading operations. 
Determination of the shortage factor should be based on constant monitoring 
of usage and prevailing conditions. 

Summary 

The standard car supply system is held to be the best approach to mini- 
mizing supply-handling problems, but it is not always applicable in the 
purest form. A simple, day-to-day, reaction-to-demand system may be more 
effective; it uses the fewest supply cars, track, and switching of any 
system. However, it also requires the maximum amount of double handling. 
In planning for and moving supplies on section, the best solution for a 
specific mine may be a combination of the two supply-handling systems. 



14 5 



Chapter 8. THE EFFECTS OF THE COAL MINE HEALTH 
AND SAFETY ACT ON RETREAT MINING 

The exact impact that the 1969 Coal Mine Health and Safety (CMH&S) Act 
has had on the ability to practice room-and-pillar retreat mining in the 
United States is impossible to determine, but it has been significant. 
Effects of the Surface Mining Act have not yet begun to be evaluated, but 
that there will be effects is a virtual certainty. In this chapter, a dis- 
cussion of the areas of Chapter 30 of the Code of Federal Regulations as of 
1979 that affect pillar extraction will be presented. The discussions will 
be divided into the following four topical areas: 

1. Roof control and ventilation plans 

2. Roof support 

3. Ventilation 

4. Electricity 

Roof Control and Ventilation Plans 

One of the requirements placed on mines performing retreat mining by the 
CMH&S Act concerns the formulation and improvement of roof control and venti- 
lation plans. These plans are submitted to and approved by the District 
Manager of the applicable Mine Safety and Health Administration (MSHA) 
District. Plans are reviewed every 6 months and must include a pillar 
recovery plan and ventilation plan of pillared areas for those mines 
practicing pillar recovery. Statements of the specific requirements of these 
plans can be found in the roof support and ventilation discussions in this 
chapter. 

The pillar recovery plan generally shows the sequence of cuts for the 
recovery of individual pillars and the sequence of pillar removal in a 
panel. The pillar recovery sequence normally shows the placement and 
sequence of roof support used during pillar extraction. In formulating 
pillar recovery plans, the mine operator should discuss proposals with the 
MSHA District roof control specialist. The specialist will frequently be 
able to suggest techniques that have worked for other mines under similar 
conditions, and at the very least, input during the initiation process will 
ease the approval process of the plan during the later stages. The 
ventilation (methane and dust control) plan shows the type and location of 
mechanical ventilation equipment and the details of the bleeder system. Once 
again, closely working with the MSHA District officials is important. State 
laws differ from Federal laws and must also be considered but will not be 
discussed in this report. 

Roof Support 

Roof support during pillar recovery is most heavily influenced by the 
CMH&S Act. The bulk of the regulations dealing with pillar recovery are 
expressed in Section 75.200-11, which is quoted below in its entirety. 



146 






s75. 200-11. Criteria — Pillar Recovery Plan 

Any reduction in pillar size during second mining 
shall be considered pillar recovery. Second mining is 
construed to be intentional retreat mining. The following 
criteria are applicable to pillar recovery roof control 
plans: 

(a) Section s75. 200-7, s75. 200-8, and s75. 200-9 
should apply depending on whether the pillar recovery plan 
calls for conventional support or a combination of conven- 
tional support and roof bolting. 

(b) During development, the size and shape of the 
pillars should be dictated by the depth of cover, height 
of coal, and other conditions associated with the coal- 
bed. The smallest dimension of the pillar should be not 
less than 20 feet. 

(c) Pillar splits and lifts should not exceed 20 feet 
in width. 

(d) A minimum of two rows of breaker posts or the 
equivalent should be installed on not more than 4-foot 
centers across each opening leading into pillared areas 
and such posts should be installed before production is 
started. Such posts should be installed near the 
breakline between the lift being started and the gob. 

(e) A row of roadside-radius (turn) posts or the 
equivalent should be installed on not more than 4-foot 
centers leading into pillar splits, including secondary 
splits in slabs, wings, or fenders. 

(f) The width of the roadway leading from the solid 
pillars to a final stump (pushout) should not exceed 14 
feet. At least two rows of posts or their equivalent 
should be set on each side of the roadway on not more than 
4-foot centers. Only one open roadway leading to a final 
stump (pushout) should be permitted. 

(g) Before full pillar recovery is begun in areas 
where roof bolts were used as the sole means of roof 
support and openings are more than 16 feet wide, supple- 
mentary support should be installed. Supplementary 
supports should consist of at least one row of posts 
installed on either side on not more than 4-foot centers 
lengthwise and limit the width of all roadways to 16 
feet. These supports should be extended from the entrance 
to the split for at least one full pillar outby the pillar 
in which the split is being made. 

(h) The following criteria should apply to open end 
pillaring: 



147 



(1) At least two rows of breaker posts or their equi- 
valent should be installed between the lift being started 
and the gob on not more than 4-foot centers before the 
initial cut is made and should be extended to within 7 
feet of the face. The width of the roadway should not 
exceed 14 feet. 

(2) If the roof in open end pillaring has a tendency 
to hang, falls should be made, or cribs installed in 
addition to the breakline posts between the active lift 
and the hanging area. The cribs should be set not more 
than 8 feet apart. Heavy duty hydraulic jacks set at 
centers close enough to give equivalent support may be 
substituted for cribs, if such jacks are removed remotely. 

Other provisions that affect pillar recovery techniques directly are 
quoted in the following material from sections s75.201, s75. 201-1, and 
s75. 201-2. 

s7 5.201. Mining Methods (Statutory Provisions) 
The method of mining followed in any coal mine 
shall not expose the miner to unusual dangers from roof 
falls caused by excessive widths of rooms and entries 
or faulty pillar recovery methods. 

s7 5. 201-1. Widths of Openings 

(a) The method of mining shall provide widths of 
openings and pillar dimensions compatible with effec- 
tive roof control. These widths and dimensions shall 
be incorporated into the roof control plan submitted 
for approval. 

(b) Where excessive widths result from poor mining 
practices, additional roof support shall be installed 
before any travel or other work is done in such area. 
If excessive widths of openings are a result of coal 
sloughing, additional support shall be installed and 
the mining system reevaluated to determine changes that 
are necessary to minimize such occurrences. 

s75. 201-2. Pillar Recovery Methods 

In addition to those criteria set forth in 
s7 5. 200-11 which may be required in the roof control 
plan, the following shall apply to pillar recovery. 

(a) The overall pillar recovery system shall be 
designed to minimize the possibility of outbursts or 
squeezes. The manner and sequence of recovery shall be 
included in the roof control plan submitted for approv- 
al. 



148 









(b) Where full pillar recovery is being done, 
extraction shall be such as to allow total caving of 
the main roof in the pillared area. 

(c) During partial pillar recovery sufficient coal 
shall be left in place to support the main roof to the 
extent that the possibility of undue forces overriding 
the working places will be minimized. 

(d) A combination of full and partial pillar 
recovery shall not be conducted on the same pillar 
line. 

(e) If full extraction of pillars is being done 
and physical conditions such as standing water, adverse 
roof conditions, and falls of roof, or law requirements 
concerning oil and gas wells or surface subsidence dic- 
tate that some pillars of coal are to be left in place, 
a sufficient amount of coal shall be left to support 
the main roof so as to minimize the possibility of 
undue forces overriding the working places. 

(f) Where full recovery of pillars is planned, the 
design of the pillars shall be compatible with the 
planned method of extraction. 

(g) Pillaring methods shall eliminate pillar 
points and pillars that project inby the breakline. 

(h) When recovering adjacent pillars left and 
right from the same opening, mining shall be completed 
in one such pillar lift and the openings posted off 
with at least two rows of breaker posts on not more 
than 4-foot centers before operations are started in 
the second pillar. 

It should be emphasized that the roof support required in any particular 
mine is heavily dependent on the MSHA District Office. The officials at the 
district office will be relying heavily on their past experiences with other 
mines operating under similar conditions. If individuals at a particular 
mine desire to try methods that have not been proven in that area, they may 
encounter stiff resistance. In such cases, it is best to have as much 
analytic support for the methods to be tried as can be obtained. 

Ventilation 

Major changes have taken place in the ventilation patterns of most mines 
practicing pillar recovery since the CMH&S Act came into effect. The basic 
ventilation requirements are expressed in paragraph 75.301 and apply to both 
advance and retreat operations. 



149 



S75.301. Air Quality, Quantity, and Velocity 

All active workings shall be ventilated by a current 
of air containing not less than 19.5 volume per centum of 
oxygen, not more than 0.5 volume per centum of carbon 
dioxide, and no harmful quantities of other noxious or 
poisonous gases; and the volume and velocity of the 
current of air shall be sufficient to dilute, render 
harmless, and to carry away, flammable, explosive, 
noxious, and harmful gases, and dust, and smoke and 
explosive fumes. The minimum quantity of air reaching 
the last open crosscut in any pair or set of developing 
entries and the last open crosscut in any pair or set or 
rooms shall be 9,000 cubic feet a minute, and the minimum 
quantity of air reaching the intake end of a pillar line 
shall be 9,000 cubic feet a minute. The minimum quantity 
of air in any coal mine reaching each working face shall 
be 3,000 cubic feet a minute. The authorized represen- 
tative of the Secretary may require in any coal mine a 
greater quantity and velocity of air when he finds it 
necessary to protect the health or safety of miners. In 
robbing areas of anthracite mines, where the air currents 
cannot be controlled and measurements of the air cannot 
be obtained, the air shall have perceptible movement. 

Details of air measurement locations are further delineated in paragraph 
75.301-3. 

s7 5. 301-3. Locations of Air Measurements 

The locations at which the quantity of air shall be 
measured are as follows: 

(a) When a single split of air is used the volume of 
air shall be measured at the last open crosscut in a pair 
or set of developing entries or the last open crosscut in 
any pair or set of rooms which shall be the last crosscut 
through the line of pillars that separates the intake and 
return air courses. When the split system of ventilation 
is used, the volume of air shall be measured in the last 
open crosscut through the line of pillars that separates 
the intake and return air courses of each split. 

(b) The volume of air at the intake end of a pillar 
line ventilated by a single split of air, shall be meas- 
ured in the intake entry furthest from the return air 
courses and immediately outby the first open crosscut 
outby the line of pillars being mined. When a split 
system of ventilation is used, the volume of air shall be 
measured inby the last intake air split point. 

(c) When longwall mining is practiced, the volume of 
air shall be measured in the intake entry or entries at 



150 



the intake end of the longwall face and the longwall 
shall be constructed as a pillar line. 

(d) The volume of air reaching each working face 
shall be measured at the inby end of the line brattice or 
other approved device. 

The bleeder systems requirements are expressed in paragraphs (e) , (f ) , 
(g) , and (i) of s75. 316-2 and in s75.329. 

s75. 316-2. Criteria for Approval of Ventilation System 
and Methane and Dust Control Plan 

(e) Bleeder entries f bleeder systems or equivalent 
means should be used in all active pillaring areas to 
ventilate the mined areas from which the pillars have 
been wholly or partially extracted, so as to control the 
methane content in such areas. Bleeder entries or 
bleeder systems established after June 28, 1970, should 
conform with the requirements of this s7 5. 316-2. 

(1) Bleeder entries shall be defined as special 
aircourses developed and maintained as part of the 
mine ventilation system and designed to continuously 
move air-methane mixtures from the gob, away from 
active workings and deliver such mixtures to the 
mine return aircourses. Bleeder entries should be 
connected to those areas from which pillars have 
been wholly or partially extracted at strategic 
locations in such a way to control airflow through 
such gob area, to induce drainage of gob gas from 
all portions of such gob areas and to minimize the 
hazard from expansion of gob gases due to 
atmospheric pressure change. 

(2) Bleeder systems shall include any combina- 
tion of bleeder entries, bleeder entry connections 
to any area from which pillars are wholly or 
partially extracted and all associated ventilation 
control devices. Such systems should extend from 
active pillar line of such gob to the intersection 
of that bleeder split with any other split of air, 
and shall not include active workings. 

(f) (1) Bleeder entries developed after June 28, 
1970 should be adequately maintained and free of 
water to permit safe travel or, if such bleeder 
entries cannot be traveled without exposing the mine 
examiner to undue hazard, such bleeder system should 
be designed and maintained so that bleeder entry 
performance can be evaluated for adequacy and 
continuity by a means approved by the Coal Mine 
Safety District Manager. 



151 



(2) When the mine operator deems that safe 
examination can be made such examination should be 
made at least once each week by a certified person 
designated by the operator to do so and the results 
of such examinations shall be recorded in a book as 
prescribed in s75.305. The certified person shall 
place his initials, the time and date at as many 
locations in the bleeder entries as are necessary to 
indicate that the entire length has been examined. 

(3) When bleeder entry travel is considered 
unsafe, the evaluation of bleeder entry performance 
should be adequate to indicate that the bleeder 
system is functioning as specified in s75. 316-3 (e) 
(1) and shall be made at least once each week by a 
certified person or persons and the results shall be 
recorded in a book as prescribed in s75.305. To 
protect the safety of the miners when bleeder entry 
performance evaluation requires altering the normal 
airflow through the affected area, such evaluation 
should be made during idle shifts with power cut off 
from the affected area. Due precaution should be 
taken so as not to endanger any other area of the 
mine and suitable examinations for methane should be 
made at the edges of the pillar and such other 
places as may be required. 

(g) The ventilation pressure differential between 
the active pillar line and the junction of any bleeder 
connection to the bleeder entries of such system should 
at all times be adequate to ensure gob gas drainage to 
the bleeder entries. The pressure differential shall be 
considered adequate when perceptible airflow exists in 
all open or regulated bleeder connections, as determined 
with chemical smoke or other approved means. 

(h) The methane content of the air current in the 
bleeder split at the point where such split enters any 
other air split should not exceed 2.0 volume per centum. 

(i) When the return aircourses from all or part of 
the bleeder entries of a gob area and air other than that 
used to ventilate the gob area is passing through the 
return aircourses, the bleeder connectors between the 
return aircourses and the gob shall be considered as 
bleeder entries and the concentration of methane should 
not exceed 2.0 volume per centum at the intersection of 
the bleeder connectors and the return aircourses. 

s7 5.329. Bleeder Systems 

On or before December 30, 1970, all areas from which 
pillars have been wholly or partially extracted and 



152 



abandoned areas as determined by the Secretary or his 
authorized representative, shall be ventilated by bleeder 
entries or by bleeder systems or equivalent means, or be 
sealed, as determined by the Secretary or his authorized 
representative. When ventilation of such areas is re- 
quired, such ventilation shall be maintained so as 
continuously to dilute, render harmless, and carry away 
methane and other explosive gases within such areas and 
to protect the active workings of the mine from the 
hazards of such methane and other explosive gases. Air 
coursed through underground areas from which pillars have 
been wholly or partially extracted which enters another 
split of air shall not contain more than 2.0 volume per 
centum of methane, when tested at the point it enters 
such other split. When sealing is required, such seals 
shall be made in an approved manner so as to isolate with 
explosion-proof bulkheads such areas from the active 
workings of the mine. 

s75. 329-1. Sealing or Ventilation of Pillared or 
Abandoned Area 

(a) All areas of a coal mine from which the pillars 
have been wholly or partially extracted and abandoned 
areas shall be ventilated or sealed by December 30, 
1970. For those coal mines in which ventilation can be 
maintained so as to continuously dilute, render harmless 
and carry away methane and other explosive gases within 
such areas and to protect the active workings of the mine 
from hazards of such methane and other explosive gases, 
the operator shall request permission from the Coal Mine 
Safety District Manager in whose district the mine is 
located to ventilate such areas. 

(b) The request for permission to ventilate such 
areas must be submitted in time to allow consideration of 
the request, to obtain approval, and to permit the opera- 
tor to install the ventilation system, or to install 
seals in the event the request to ventilate is denied, on 
or before December 30, 1970. 

(c) The determination of whether ventilation will be 
permitted will be made after taking into consideration 
the history of methane and other explosive gases in the 
mine, the size of the gob or abandoned areas, and if the 
areas can be ventilated adequately. 

(d) To be considered for approval the request shall 
contain the following information provided by the mine 
operator. 



153 



(1) Name of mine and company. 

(2) Location of mine (town, county, state) . 

(3) Operator's name and address. 

(4) Date of application. 

(5) A detailed history of the methane content 
determined throughout the mine and when 
available, the volume of air in which such 
methane determinations were made, to support 
the operator's application to ventilate. 

(e) A description of the method by which the areas 
from which the pillars have been wholly or partially 
extracted and abandoned areas shall be ventilated and 
such maps and drawings as may be required to illustrate 
such method and to indicate existing or proposed air 
volumes used to ventilate such areas. 

(f) The signature and title of the person who 
submits the application for the operator. 



An extensive discussion of bleeder systems was presented in Chapter 6, 
Mine Planning and Retreat Mining, and will not be repeated. However, it 
should be emphasized in the context of the effects of the law on retreat 
mining that the establishment and maintenance of bleeder systems is of 
primary importance to the operation and success of pillar recovery. It must 
also be stated that in some cases, the difficulty involved in establishing 
and maintaining bleeder systems and their impact in the amount of recoverable 
reserves has been a deciding factor in a mine's decision to practice retreat 
mining. The extent of the bleeder systems required will depend on the gas 
liberation levels and various mining conditions such as roof type and 
tightness of fall. The best indication of requirements for the bleeder 
system will normally be found in observing operations in the other mines 
operating in the area. In areas where spontaneous combustion is a problem, 
it is frequently more desirable to seal pillared areas than to attempt to 
bleed them. 

Other than the effects felt due to bleeder systems, ventilation require- 
ments unique to retreat mining have not been extensive. Of course, the coal 
dust and gas level requirements must be complied with as they were on ad- 
vance. However, on retreat, most of the gas has already bled off and coal 
dust is generally less significant compared with the conditions experienced 
on advance. 

Electricity 

The vast majority of regulations governing the conditions of electricity 
use in coal mines do not affect retreat mining per se. One paragraph, 
s75.1002, limits the placement of trolley wires, trolley feeder wires, and 
high voltage cables to locations at least 150 feet away from pillar workings. 



154 



S75.1002. Location of Trolley Wires, Trolley Feeder 

Wires, High-Voltage Cables and Transformers 

Trolley wires and trolley feeder wires, high-voltage 
cables and transformers shall not be located inby the 
last open crosscut and shall be kept at least 150 feet 
from pillar workings. 

s7 5. 1002-1. Location of Other Electric Equipment; 
Requirements for Permissibility 

(a) Electric equipment other than trolley wires, 
trolley feeder wires, high-voltage cables, and trans- 
formers shall be permissible, and maintained in a 
permissible condition when such electric equipment is 
located within 150 feet from pillar workings, except as 
provided in paragraphs (b) and (c) of this section. 

(b) Notwithstanding the provisions of paragraph (a) 
of this section, in any coal mine where nonpermissible 
electric face equipment may be taken into or used inby 
the last open crosscut until March 30, 1974, such non- 
permissible electric face equipment may be located within 
150 feet from pillar workings. 

(c) Notwithstanding the provision of paragraph (a) 
of this section, in any coal mine where a permit for 
noncompliance is in effect, nonpermissible electric face 
equipment specified in such permit for noncompliance may 
be located within 150 feet from pillar workings for the 
duration of such permit. 



15 5 



Chapter 9. DE'TELOPING A SECTION FOREMAN'S GUIDEBOOK 

Introduction 

Each mine operates in a somewhat different environment, geotechnically 
and organizationally, than other mines in the same general area. Because of 
this fact, it is highly unlikely that a comprehensive, all-encompassing 
guidebook for section foremen could be developed for general application. 
Rather, each company should design its own guidebook, to address specifically 
the operations and conditions of its particular mines. Increasingly, indi- 
vidual companies are developing their own guidebooks for foremen. Many were 
encountered during this study — varying in quality but all successful in their 
applicaton. It is the purpose of this section to present a method for the 
development and use of mine-specific section foreman guidebooks. This method 
can be used for developing handbooks for engineering groups or other technical 
persons. 

Purpose of Guidebooks 

Guidebooks should serve as reference sources for foremen, giving perti- 
nent information concerning the mining method used on the section involved. 
They should not be used as a substitute for proper training or for direct 
interaction and communication with mine management. They should not super- 
sede or conflict with any existing State or Federal mining laws. Further, 
they should not supersede approved mining projection maps at any time with 
regard to room depths or crosscut locations. 

Proper use of guidebooks allows for some standardization in an extremely 
variable environment. The ultimate objective of such standardization is 
safer mining practices and increased productivity. With this objective comes 
cost efficiencies in terms of time and materials and, of course, increased 
output. 

Introducing the Guidebook Concept to Foremen 

The first and by far the most important step in the creation of a guide- 
book is to introduce the guidebook concept. The concept must have the sup- 
port of the intended user or it will not be used. 

It is highly recommended that guidebook users be involved in its prepara- 
tion and be trained in guidebook usage. Some ways of achieving these objec- 
tives include — 

1. Involving foremen at the beginning in the actual design and 
structuring of the guidebook. 

2. Requesting comments and suggestions from a panel of foremen reviewing 
the draft guidebook. 

3. Conducting seminars or workshops that present simulated problems and 
require the guidebook as a reference source to solve the problems. 

4. Using the guidebook as a training tool and part of formal aboveground 
classroom training. 



156 



The key is involvement. Foremen who participate in the development of a 
guidebook will feel a commitment to the final product. Under these condi- 
tions the guidebook is more likely to be accepted and used if its presence is 
not viewed as an upper management directive but rather as a foreman's guide- 
book developed by foremen. Acknowledgments that specifically identify par- 
ticipants and contributors can be a very positive gesture toward achieving 
this commitment. 

A final point to be made is that completely successful implementation of 
a guidebook will require an introductory an training program that requires 
the foremen to use the book. One suggested approach is to tie the intro- 
duction and formal training of guidebook use to the formal training at the 
mine. This approach may be least disruptive and will integrate well with 
other training topics routinely covered during foreman training sessions. 

Developing the Guidebook Outline 

A topical outline for the guidebook should be developed to assist in the 
organization and writing of the guidebook. This simple but often neglected 
exercise can save an immense amount of time and money and ensure that all 
important topics are covered in the guidebook. The level of detail in an 
outline should be sufficient to identify specific task areas for easy ref- 
erence. The outline is essentially a table of contents of the guidebook; an 
example of parts of a retreat mining guidebook to which foremen can refer 
follows. 

Example Outline: Foreman's Retreat Mining Guidebook 

I. General information 

II. Sequence of mining and entry and room dimensions 

A. Panel development 

B. Bleeder connections 

C. Room development 

D. Room-and-pillar recovery 

E. Chain pillar recovery 

III. Equipment operation 
A. Continuous miner 

1. Pre-shift safety inspections and servicing 

a. Checking power and cable 

b. Inspecting the continuous miner 

c. Energizing the continuous miner 

d. Inspection of work place 

e. Routine maintenance 

2. Continuous miner operations 



157 



a. Tramming the miner on retreat sections 

b. Setting temporary supports in each place 

B. Roof bolts 

IV. Belt moves and placement 

V. Free cuts and posting 

VI. Ventilation 

VII. Haulage 

VIII. The effects of the Coal Mine Health and Safety Act on retreat mining 

A. Roof control and ventilation plans 

B. Roof support 

1. s75. 200-11. Criteria — Pillar Recovery Plan 

2. s7 5. 201-2. Pillar Recovery Methods 

C. Ventilation 

1. S75.301. Air Quality, Quantity, and Velocity 

2. s75. 301-3. Locations of Air Measurements 

3. s75.329. Bleeder Systems 

4. s75. 329-1. Sealing on Ventilation of Pillared or 

Abandoned Area 

D. Electricity 

1. S75.1002. Location of Trolley Wires, Trolley Feeder Wires, 

High-Voltage Cables and Transformers 

2. s75. 1002-1. Location of Other Electric Equipment; Requirements 

for Permissibility 



Although this guidebook outline focuses on retreat mining operations, a 
foreman's handbook should cover all aspects of panel mining, including both 
development and retreat work. 

Selecting the Format of the Guidebook 

Guidebooks should be clearly and concisely written and organized in such 
a way as to make them easily usable. A format that allows for rapid and easy 
identification of relevant topics is essential as well. Again, the purpose 
of a guidebook is ready reference, so rapid access to topical areas of inter- 
est is a major factor in guidebook design. 

Another consideration in format selection is the physical structure and 
appearance of the guidebook. Innumerable options are available. For 



158 



example, sizes can vary from pocket size to even larger than the standard 
8-1/2 by 11-inch reproducible bond. The guidebook may be produced in a bound 
form (hard or soft cover) or in some form of loose leaf notebook. In this 
latter format, individual sections can be taken from the main body and used 
as necessary. 

Assembling the Information 

In preparing a guidebook, it is important to be detailed and comprehen- 
sive. Therefore, complete information on each topic to be covered in the 
guidebook is a must. Collecting the information from those in the company 
most familiar with each topic is probably the most cost effective and timely 
approach. For example, information related to panel and section dimensions 
is best obtained from the engineering group; labor relations data are best 
obtained from the personnel department. Of course, regulations can usually 
be obtained from several in-house sources or directly from regulating 
agencies. 

Improving and Updating the Guidebook 

Probably the greatest problem in gaining acceptance and routine use of 
guidebooks over the long term is that they become outdated. Regulations 
change, mining conditions change, labor relations change, equipment changes, 
and mining techniques change. Thus, ongoing guidebook maintenance is just as 
important as routine continuous miner maintenance. 

The necessity of improvements and updates, more than any other, requires 
a guidebook format that can be updated with new information. Reprinting 
entire guidebooks periodically is a much less effective means and would not 
get the new information disseminated nearly as rapidly as routine update 
sheets. With a loose leaf notebook format, old sheets can be discarded as 
new ones are issued. New and revised sheets should be so noted in a covering 
letter, and the date of issue of the revision should be indicated near the 
page number of the newly revised sheet. This ensures that the reader can 
determine if his copy contains the latest information. 



159 



ANNOTATED BIBLIOGRAPHY 



Adler, L. , and J. L. Gallimore. The Need for a New Mining System. Min. 
Cong. J. , September 1972, pp. 24-29. 

This article provides a general description of both the development and 
retreating phases of room-and-pillar mining. A cut sequence for wing and 
pocket pillaring and a pillaring sequence for mining rooms and a single row 
of blocks with a continuous miner are illustrated. However, because of the 
disadvantages of the room-and-pillar system, a retreat mining system 
combining the longwall and room-and-pillar methods is described and 
recommended. 



Adler, H. , S. W. Potts, and A. Walker. Mechanized Room-and-Pillar Mining: 
A General Appreciation of Developments in Great Britain. Trans. Inst. Min. 
Eng. (London), v. 110, 1950-51, pp. 728-740. 

Available information from the coalfields regarding room-and-pillar work is 
summarized, and developments are described with respect to (1) normal 
development of previous practice and (2) recent adoption without reference to 
previous practice. Details are given of a representative selection of 
mechanized room-and-pillar installations considered to be giving the best 
results, and the lessons to be learned from the experience gained are stated. 



Asman, A. W. , and A. W. Bitner. Characteristics of Mechanized Mining Sec- 
tions. Min. Eng., September 1951, pp. 803-804. 

An analysis is made of three different types of section production units 
that represent the manner in which most of the Nation's bituminous coal is 
produced. The general delays and production characteristics of these sec- 
tions are presented along with a method for evaluating section performance 
based on actual and theoretical production characteristics. 



Bise, C. F. , R. V. Ramani, and R. Stefanko. An Analysis of Underground 
Extraction Techniques for Thick Coal Seams. Coal Research Station, The 
Pennsylvania State University, University Park, SR-111, 1976, 209 pp. 

This document provides a general description of thick-seam methods and a 
description of actual mining operations in North America. Several mining 
methods are recommended, including a room-and-pillar method. Safety 
factors are briefly discussed. 



Bobo, B. L. Experience With Continuous Miners at Mathies. Min. Cong. J., 
July 1966, pp. 30-36. 

This article describes the pocket-and-f ender method of pillar extraction 
with continous miners used at the Mathies mine in Pennsylvania. 



160 



Campbell, J. A. L. , L. J. Petrovic, W. J. Mallio, and C. W. Schulties. How to 
Predict Coal Mine Roof Conditions Before Mining. Min. Eng., October 1975, 
pp. 37-40. 

Geological modeling, lineaments, and construction of a geologic model to 
predict roof conditions are discussed. The use of overlays are used to 
depict data graphically. 



Canadian Mines Branch, Department of Energy, Mines and Resources, Proceedings 
of the 9th Canadian Rock Mechanics Symposium, Ottawa, Canada, 1974. 

This document includes a statement of the Holland-Gaddy formula for coal 
pillar design, a review of the mine examination required with practical 
suggestions as to what to look for and how to do it, and a review of 
several pillar design formulas recently suggested and a comparison of each 
with the other as to results and procedures. 



Cassidy, S. M. (ed.). Elements of Practical Coal Mining. Society of Mining 
Engineers of the American Institute of Mining, Metallurgical, and Petroleum 
Engineers, Inc., New York, 1973, 614 pp. 

Ventilation and dust control, development mining, retreat mining methods, 
pillar lines, partial extraction, multiple-seam mining, and pitching seams 
are among the topics covered in this handbook. 



Chauhan, N. P. Extraction of a Thick Seam in Chirimiri Coalfield Using 
Trolly Wire Locomotives. J. Mines Met. and Fuels, November 1971, pp. 
335-339. 

This article deals with the problem of extracting thick seams developed 
in the past, with some coal left in roof and floor. The method presented 
is to extract pillars by slicing with open goat, up to a height of 5.4 
meters using trolley wire locomotives and mine cars right up to the stooks 
under extraction. The thickness of the seam varies from 6 to 9 meters, 
with past developments of 3 to 4 meters in height in the area under 
extraction. The gradient of the seams is nearly flat with a strong roof of 
massive sandstone. 



Chironis, N. P. Peabody Mine's Serpentix Boosts Mining Output. Coal Age, 
April 1977, pp. 58-64. 

This article describes the serpentix haulage system (a belt conveyor system 
suspended from monorail track attached to the roof by conventional roof bolts) 
used in a mine having a room-and-pillar mining plan. 



161 



Coal Age. Be osting Mining Efficiency. December 1955, pp. 50-55. 

This article describes the mine conditions at the Buckhorn mine, 111., the 
tillar recovery method used, and the roof support and roof coating systems 
applied. 



. Bulk of US Underground Coal Production Still Issues from Room-and- 

lillar Work. July 1976, pp. 110-113. 

A six-entry room-and-pillar section using two miners and two bolters is 
described. Advantages include a substantial savings of tramming time and a 
reduction in abnormal delays in the cycle. Research on a continuous miner 
equipped with a bolter conveyor and remote control is also discussed. 



Continuous Mining. July 1971, pp. 160-164. 



Continuous mining equipment and systems, including room-and-pillar 
mining, are discussed. 



Conventional Mining. July 1971, pp. 169-173. 



Conventional mining is described with respect to equipment selection, 
conventional system?, and face preparation, including pillar lines and 
pillaring plans. 



Hanging Ventilation Curtains. November 1978, pp. 111-115. 



This article describes a technique for hanging air curtains that permits 
them to be installed, moved, opened, and closed more easily than when they 
are nailed or spadded in place. The technique involves the use of low- 
leakage, low-cost plastic curtains threaded onto a steel cable that is 
suspended from roof bolt plates by S-shaped hooks. The outby end of the 
cable is reeled off a hand-operated winch; the inby end of the cable is 
anchored to a roof bolt plate by means of a cable grip and an S-shaped 
hook. 



High Tonnage With Small Crews. September 19 56, pp. 60-63. 



Open-end pillaring with a continuous miner at the Isabella mine, Penn- 
sylvania, is described. Included in the discussion are roof support 
details, a two-pass mining system, and equipment used. 



Mining Guidebook. July 1972, pp. 130-158. 



Mine development (i.e., initial planning, mine projections, and entry 
driving), continuous and conventional mining equipment and pillaring 
systems, roof control, haulage and hoisting, and ventilation fundamen- 
tals are among the topics covered in this guidebook. 

162 



Mining Methods and Equipment. October 1970, pp. 100-133. 



Mining methods, including pillar extraction, and equipment; roof control 
methods; and ventilation and drainage methods practiced by various mines 
are discussed. Problems encountered and solutions provided are included. 



More Powerful Continuous Miners. April 1962, pp. 72-75. 



This article describes how more powerful and rugged continuous miners 
boost productivity. The pillaring, roof bolting, and ventilation plans for 
mining the Pittsburgh seam are also described. 



Pillar-Mining Team: Continuous Miner and Tracklaying Shuttle Car. 



July 1953, pp. 98-99. 

The recovery of Pittsburgh seam pillars sandwiched between wet fire clay 
bottom and draw slate top is described. A system is developed using a con- 
tinuous miner, a pickup loading machine, and a tracklaying shuttle car. 
Roof support work is also described. 



Pillaring With Continous Miners. October 1956, pp. 73-77. 



This article describes various aspects of and methods of pillaring with 
continuous miners, for example: stepped pillar line, combination advance 
and retreat, full retreat, angle plans, conventional open ending, angle 
open ending, splitting plans, pocket-and-wing plans, and a basic room-and- 
pillar plan modified for an extensible-belt. 



Practical Ways to Cut Coal Mining Costs. Coal Age, New York, 19 50, 



224 pp. 

This publication is a composite of articles published in Coal Age and 
organized under such headings as: mechanized coal mining; underground 
transportation; coal preparation; mine safety; and ventilation, drainage, 
and pumping. 



Preparing for Continuous Mining. May 1957, pp. 70-7 5. 



This article defines the factors that need to be considered in developing 
a mining system using continuous miners. Topics covered include: machine 
type, panel layout, plan development sequence to achieve maximum operating 
time and minimum moves for mining machine, open-end pillaring, roof 
support, ventilation, and haulage. 



163 



The Deep-Mining Guidebook. Mid-July 1958, pp. 34-57. 

Retreat operation planning (including bleeders and pillar size and 
shape) , entry driving, room plans, pillaring systems, pillar lines, and 
haulage are among the topics discussed in this guidebook. 



Corwine, J. W. Review of Roof Control Technology Research. Min. Cong. J., 
January 19 76, pp. 25-29. 

Present ground and roof control research programs in the following areas 
are described: preliminary investigations, mine layout and opening design, 
selection and application of support systems, safe installation of 
supports, hazard detection, and mining systems for improved ground control. 



Currie, R. D. , and E. R. Maize. A Ventilation Study of the Graceton Coal & 
Coke Co. Mine, Graceton, PA. BuMines IC 6614, 1932, 10 pp. 

Relevant topics covered in this article are doors, overcasts, and 
stoppings. Their construction and most effective usage are described. 



Curth, E. A. Relative Pressure Changes in Coal Pillars During Extraction: A 
Progress Report. BuMines RI 6980, 1967, 20 pp. 

This report describes the pillar extraction method used at the Nemacolin 
mine in Pennsylvania. Tests were conducted to determine the relative 
pressure changes in the coal pillars during extraction, and conclusions are 
presented. 



Flint, J. D. , and C. Taylor. Pillar Extraction With Conventional Trackless 
Mechanized Units. J. S. Afr. Inst. Min. and Met., September 1971, pp. 
47-56. 

A description is given of the pocket-and-f ender method of pillar 
extraction of a coal seam varying in thickness from 10 to 14 feet. 
Conventional, trackless, mechanized units are used to extract the coal. 



Gilley, J. L. , and E. Thomas. Pillar Extraction With Roof Bolts. Min. Cong. 
J., November 1951, pp. 30-33. 

The pillar recovery practices at a mine in southern West Virginia are 
described, and tables that compare the results of mining with conventional 
timbering to mining with roof bolting are included. 

Given, I. A. (ed.). SME Mining Engineering Handbook. Society of Mining 

Engineers of the American Institute of Mining, Metallurgical, and Petroleum 
Engineers, Inc., New York, v. 1, 1973. 



164 



Rock mechanics and other factors involved in selecting a mining method, 
roof and ground control, underground haulage, ventilation, and underground 
mining systems and equipment are relevant topics covered in this handbook. 
With respect to room-and-pillar extraction methods, bleeders, complete 
versus partial extraction, cutting approaches, and economics are discussed. 



Gooding, K. M. (comp. ) . Proceedings of the Symposium on Respirable Coal Mine 
Dust, Washington, D.C. , November 3-4, 1969. BuMines IC 8458, 1970, 297 pp. 

Pertinent papers in this document cover (1) ventilation theories and 
principles and (2) ventilation practices for dust control. 



Green, L. E. , and E. R. Palowitch. Comparative Shortwall and Room-and-Pillar 
Mining Costs. BuMines IC 8757, 1977, 20 pp. 

This report describes the room-and-pillar mining method used at a 
Beth-Elkhorn mine in Kentucky — including the pillar extraction sequence — 
and makes an economic comparison between this method and a shortwall method 
used in an adjacent mine. 



Grouch, S. L. , and C. Fairhurst. The Mechanics of Coal Mine Bumps and the 
Interaction Between Coal Pillars, Mine Roof, and Floor. BuMines Open File 
Rept. 53-73, 1973, 88 pp.; available for references at Bureau of Mines 
facilities at Pittsburgh, Pa., Denver, Colo.; Spokane, Wash., and Twin 
Cities, Minn.; and at the Central Library, U.S. Department of the Interior, 
Washington, D.C. 

This report describes the circumstances likely to be responsible for coal 
mine bumps. Studies predict that a large bump would be less likely in 
longwall mining. However, since this type of mining cannot always be 
carried out, a pillaring system that limits the amount of development prior 
to pillar extraction is recommended. Procedures for accomplishing this are 
provided. 



Haley, W. , J. J. Shields, A. L. Toenges, and L. A. Turnbull. Mechancial 
Mining in Some Bituminous Coal Mines. Progress Report 6. Extraction of 
Pillars With Mechanized Equipment. BuMines IC 7631, 1952, 64 pp. 

General discussions on recovery in coal mining and roof action and 
control are followed by descriptions of mines and the mining and pillar 
extraction methods used by each. 



Hazen, G. , and L. Artier. Practical Coal Pillar Design Problem. Min. Cong. 
J., June 1976, pp. 86-92. 

This article describes the tests conducted on coal pillars to determine 
their strength und§r stress. The higher stresses were found on the inside 



165 



of each pillar and the lower stresses fell to the outside. The general 
trend depicted was that the specimens became stronger as the became larger. 



Herbert, C. A. Some Factors Affecting and Suggested Ways for Improving Coal 
Mine Ventilation, With Particular Reference to Mines in Illinois, Indiana, 
and Western Kentucky. BuMines IC 7656, 1953, 15 pp. 

The causes of explosive methane accumulations in mines discussed are lack 
of well-maintained air courses; air losses due to leaky stoppings, trap 
doors, and overcasts; faulty mining methods; and poor supervision. A 
modified room-and-pillar mine development plan is suggested to eliminate 
many of the hazards of gas accumulations inherent in the present method of 
mine development. 



Hess, W. E. Pillar Extraction in the Pittsburgh Seam With Continuous Miners. 
Min. Eng. , February 1955, pp. 162-166. 

This article describes the advantages of using the continuous miner 
instead of conventional mining in pillar extraction. 



Hittman Associates, Inc. Underground Coal Mining: An Assessment of Tech- 
nology. Electric Power Research Institute, Palo Alto, Calif., EPRI AF-219, 
July 19 76. 

This report includes two pertinent sections — Underground Coal Mining 
Today, and Interrelationship and Constraints in Underground Mining. Topics 
discussed in these sections include mine development, room-and-pillar 
mining systems, pillar sizes, loading and hauling, production variables, 
conventional and continuous mining equipment advantages and disadvantages, 
ground control, pillar stresses, roof support, ventilation, and mine 
drainage. 



Hoard, C. M. , and C. S. Cressman. Full Pillaring With the Boring-Type Miner. 
Coal Age, March 1959, pp. 74-78. 

An increase in production at Mine No. 41 of the Bethlehem Mines Corp. in 
West Virginia is attributed to use of a boring-type miner for pillaring, 
adoption of slabbing as the pillar-extraction method, a change from a 
45-degree to a flat pillar line (good illustration of the differences 
provided here) , and the adoption of a rope-frame panel belt to cut delay 
time to the absolute minimum. 



Holland, C. T. Factors in the Design of Barrier Pillars in Coal Mines. 
Proc. W. Va. Coal Min. Tnst., Morgantown, W. Va. , 1965, pp. 109-126. 

This paper is confined to factors affecting the design of those pillars 
left in a coal mine to delimit the stress effects produced by mining 
operations. 



166 



The Strength of Coal in Mine Pillars. Proc. 6th Symp. Rock Mech. , 



Univ. Mo., Rolla, Mo. , 1964. 

Discussed in this article are experiments relating to pillar size and 
strength, a proposed coal pillar strength formula, and verification of the 
formula's reliability. 



Holland, C. T. , and F. L. Gaddy. Some Aspects of Permanent Support of Over- 
burden of Coal Beds. Proc. W. Va. Coal Min. Inst., Morgantown, W. Va. , 
1956, pp. 43-65. 

This paper discusses some of the factors involved in determining the 
amount of coal that should be left in a mine to provide permanent support 
for overburden. 



J. J. Davis Associates. Study of Methods to Improve Pillar Extraction Prac- 
tices in Underground Coal Mines: Part III, Rock Mechanics. Preliminary 
rept. prepared for BuMines under contract USBM HO242007, 1975, 111 pp.; 
available from J. J. Davis Associates, McLean, Va. 

This preliminary report determines the principal factors contributing to 
high accident frequency and severity in both conventional and continuous 
mining operations. It also compares and evaluates the safety aspects of 
the open-end and split-and-fender systems of pillar mining. Basic data 
required to decide what constitutes an adequate pillaring plan that will 
optimize efficiency, recovery, and safety is established. Recommendations 
are made to improve existing pillaring methods and to ensure that proper 
techniques are implemented. Areas where additional studies or new research 
may be of value are suggested. 



Study of Methods to Improve Pillar Extraction Practices in Under- 



ground Coal Mines: Volume 1, Pillar Safety and Production Practices. J. 
J. Davis Associates, McLean, Va., 1975. 

This report covers pillar extraction methods and practices and provides 
recommendations for improving pillar extraction. Also covered are rock 
mechanics of pillar extraction and accident analysis. 



Johnstone, J. Recent Developments in Underground Mining in Australia. 3rd 
Symp. on Underground Mining. National Coal Association, Washington, D.C. , 
1977, pp. 9-24. 

This paper describes bord or pillar mining in New South Wales and the Old 
Ben and Wongawilli systems of room and pillar mining. 



Jones, D. C. Pillar Extraction With Continuous Mining Machines. Mechaniza- 
tion, December 1955, pp. 54-59. 



167 



This article describes the pillar extraction method used at the 
Lancashire No. 15 mine in Pennsylvania. Topics discussed include 
timbering, ventilation, safety, production, and continuous miners. 



Kalasky, J. D., and S. Krickovic. Ventilation of Pillared Areas by Bleeder 
Entries, Bleeder Systems, or Equivalent Means. Trans. Soc. Min. Eng. , 
AIME, v. 254, December 1973, pp. 284-290. 

The fundamentals of effective bleeding for provision of good ventilation 
and control and removal of methane are described. The various mine pillar- 
ing systems for which it is both easy and difficult to provide effective 
bleeder systems are detailed. 



Keenan, A. M. Pillar Extraction Methods Developed at Kenilworth. Mechaniza- 
tion, August 1949, pp. 50-59. 

The successful extraction of pillars at the Kenilworth mine in Utah is 
described in great detail. Topics covered include mine conditions, mine 
layout, pillar extraction (including the advantages of a 45-degree line) , 
roof support, machinery, haulage, and ventilation. The problem of 
spontaneous combustion of coal near the surface is dealt with. 



Kharkar, R., R. V. Ramani, and R. Stefanko. Analysis of Leakage and Friction 
Factors in Coal Mine Ventilation Systems. Pennsylvania State University, 
University Park, Pennsylvania, SR-99, April 1974, 73 pp. 

Relevant information contained in this document is a description of the 
coal mine ventilation systems in the United States. 



Kingery, D. S. Introduction to Mine Ventilating Principles and Practices. 
BuMines Bull. 589, 1960, 54 pp. 

This bulletin is written to explain in layman language the basic laws and 
fundamentals of mine air flow and their application to the solution of 
common ventilation problems. 



Krisko, W. J. Evaluation of the Use of Air Curtains to Increase Face Venti- 
lation. BuMines Open File Rept. 157-77, 1977, 126 pp.; available for 
reference at Bureau of Mines facilities at Denver, Colo., Twin Cities, 
Minn., Bruceton and Pittsburgh, Pa., Spokane, Wash.; Department of Energy 
facilities at Carbondale, 111., and Morgantown, W. Va.; at the Central 
Library, U.S. Department of the Interior, Washington, D.C.; and from the 
National Technical Information Services, Springfield, Va., PB 274 324/AS. 

Laboratory and in-mine tests were used to determine the feasibility of 
using an air curtain in place of brattice cloth to separate incoming air 
from exhaust air at the face of a room-and-pillar underground coal mining 
operation. Laboratory experiments proved that the concept of an air 



168 



curtain separating two parallel streams of air is valid. The in-mine tests 
consisted of measuring respirable dust concentrations at the operator's 
position both with and without the air curtain. These tests demonstrated 
that the installed air curtain could act as effectively or more effectively 
than line brattice in coursing air to the working face. 



Laird, W. Pillar Extraction in High Coal. Mechanization, April 1963, 
pp. 31-21. 

The pillar extraction method used at the Federal No. 1 mine in West 
Virginia is described. 



Luxner, J. V. Face Ventilation in Underground Bituminous Coal Mines. 
Airflow and Methane Distribution Patterns in Immediate Face Area-Line 
Brattice. BuMines RI 7223, 1969, 16 pp. 

The effectiveness of face ventilation by line brattice is reviewed with 
respect to the method of ventilation (i.e., blowing and exhausting), the 
face distance, the tight rib distance, the volume of air delivered to the 
end of the line brattice, and the volume of methane released at the face. 
Analysis of data are based upon the ability of a face ventilation system to 
dilute methane in the immediate face area. 



Mason, R. H. Amherst Boosts Production 50% With Continuous Haulage System. 
Coal Min. and Proc. , August 1977, pp. 52-57. 

The continuous haulage system installed by Amherst Coal Co. utilizes 
conveyor belting in the bridge conveyors and mobile bridge carries. This 
system allows for 90 to 95 percent recovery on pillaring, and the entire 
pillar can be extracted without moving the haulage system. 



. How a Small Operator Gets Big Productivity. Coal Min. and Proc. , 

July 1978, pp. 66-71. 

The Mason Coal Co. achieves high productivity with a continuous miner and 
continuous haulage system. A description of the room-and-pillar advance 
and retreat mining system used by the company is given. 



National Coal Board. Memorandum on the Design of Mine Workings to Secure 
Effective Strata Control. Trans. Inst. Min. Eng. (London) , v. 110, 1951, 
pp. 252-271. 

This article sets out, in a very understandable fashion, guiding 
principles for the design of mine workings to reduce loads in the working 
area. It is suggested that concentrations of main roof load in working 
areas can be avoided by the controlled transference of load if proper 
provision is made for the accommodation of the concentrated abutment loads 
on coal pillars of adequate dimensions or in excavated areas in positions 



169 



clear of the roadways. The behavior of coal pillars is discussed and 
pillar dimensions are related to the widths of the adjoining excavations. 
The foregoing considerations are applied to, among others, the design of 
mechanized room-and-pillar workings. 



Norris, W. , Jr. Pillaring Operations With Continuous Mining Machines Under 
Bumping Conditions. Min. Cong. J., March 1960, pp. 41-43. 

Bumping problems experienced at two mines in West Virginia and experi- 
ments toward a solution when mining pillars with continuous mining machines 
are discussed. 



Palowitch, E. R. Underground Coal Mining Research. Min. Cong. J., February 
1978, pp. 34-41. 

The underground coal mining research and state of the art in 1977 is 
desribed with respect to mine planning, design and development, convention 
systems, room-and-pillar mining, advanced systems, and health and safety. 



Parker, J. Practical Rock Mechanics for Miners, Parts 1 through 7. Eng. and 
Min. J. , June through December, 1973, and January through February, 1974. 

This series of articles describes simple, inexpensive, money-saving 
approaches to problem solving in the field of rock mechanics based on the 
built-in knowledge and experience of mine operators. Topics covered are 
surface subsidence; convergence measurements; relationship between 
structure, stress, and moisture; design of mine openings; roof support; and 
pillar design. 



Peng, S. S. Coal Mine Ground Control. John Wiley & Sons, New York, 1978, 
450 pp. 

This document is to be used as a textbook on roof control of underground 
coal mine openings. It stresses the practical application of various tech- 
niques. In addition to discussions on topics such as coal pillars, room- 
and-pillar mining is covered specifically with respect to typical section 
layout, room or entry development, and pillar recovery. 



Peng, S. S., and U. Chandra. Getting the Most From Multiple-Seam 
Reserves. Coal Min. and Processing, November 1980, pp. 78-84. 

This article presents the results of a study of 20 West Virginia mining 
operations that deal with multiple seams. Information on mining problems 
encountered and the circumstances leading to those problems were obtained. 
The authors discuss five cases to illustrate how several typical ground 
control problems can be eliminated by the application of fundamental prin- 
ciples of ground control. Guidelines for multiple-seam mining are recom- 
mended . 



170 



R. J. Bowen Mining Engineering Consultants. Sublevel Caving by Pillar 
Extraction. U.S. Department of Energy, FE-9115-1, May 25, 1977, 160 pp. 

This report describes the design and feasiblity analysis of the Sublevel 
Caving by Pillar Extraction mining method which is a conceptual mining 
method devised toward the objective of improving mining techniques for 
extraction of deep coal occurring in seams of thicknesses greater than 12 
feet. The concept envisions that advance openings of the mine will be 
driven along the bottom of the thick seam with top coal being extracted 
incrementally during retreat mining, or in "falls," shot down from the 
roof. Loading of fallen top coal is accomplished with the loading machine 
operator remaining in a protected position. 



Reeves, J. A. Continuous Mining of Pitching Coal Seams. Min. Cong. J., 
January 1966, pp. 27-30. 

The mine conditions and mining method at the Dutch Creek mine in Colorado 
are described. Mining sequence, pillar recovery, and ventilation are 
discussed. 



Salamon, M. D. G. , and J. I. Oravecz. Rock Mechanics in Coal Mining. The 
Chamber of Mines of South Africa, Johannesburg, South Africa, 1976. 

This document describes pillar extraction methods used in South Africa 
and includes a discussion on support in bord and pillar workings and 
haulages. Rock mechanics is the main theme of the material, and 
discussions in this area include considerations in multi-seam mining and 
improving the stability of pillared areas. 



Saperstein, L. W. , G. R. Brown, J. D. Bennett, R. Murphy, F. Gilliam, and 
R. B. Anderson. New Miner Orientation Manual: An Instruction Training 
Manual. Pennsylvania State University, University Park, Pa., September 
1976. 

This instruction training manual includes such topics as coal geology, 
ventilation, roof and rib control, haulage, and accident prevention. 



Schlick, D. P. , and R. W. Dalzell. Ventilation of Continuous-Miner Places in 
Coal Mines. BuMines IC 8161, 1963, 18 pp. 

This article presents a representative cross section of methods success- 
fully used to ventilate continuous-miner places as well as various factors 
that should be considered when selecting auxilliary ventilating equipment. 



Schroder, J. L. , Jr. Continuous Miners Extract High Splint Pillars. Coal 
Age, December 1966, pp. 84-87. 

This article describes the pocket-and-wing pillar extraction method used 
to mine the High Split seam in Kentucky. The plans had to take into 

171 



account an extremely soft bottom and areas* vulnerable to bumps. Advantages 
of the system are given/ and major considerations during extraction are 
stressed. 



Shields/ J. J. , and J. J. Dowd. Mechanical Mining in Some Bituminous Coal 
Mines. Progress Report 9. Face Haulage. BuMines IC 7978, 1960/ 106 pp. 

This study concerns different methods of face haulage used with various 
types of continuous mining machines/ mobile loading machines/ and track- 
mounted equipment under varying roof and bottom conditions and in coalbeds 
of varying thicknesses. Face haulage methods used in 13 mines in Pennsyl- 
vania/ West Virginia/ Ohio, and Illinois are studied and compared. 



Shields, J. J. , J. J. Dowd, and W. A. Haley. Mechanical Mining in Some 
Bituminous Coal Mines. Progress Report 8. Methods and Equipment Used in 
Underground Development. BuMines IC 7813, 1957, 66 pp. 

Methods and equipment used in underground bituminous coal mine devel- 
opment in 14 mines were studied to determine how the application of modern 
methods and equipment affect the rate of entry development. The study 
revealed a tendency toward equalization of the output per man between 
development and production. 



Shields/ J. J. , M. 0. Magnuson/ W. A. Haley, and J. J. Dowd. Mechanical 
Mining in Some Bituminous Coal Mines. Progress Report 7. Methods of 
Mining With Continuous Mining Machines. BuMines IC 7696, 1954, 118 pp. 

A description of mines and the mining and pillar extraction methods used 
by each with continuous mining methods is provided. 



Snarr, F. E. A Complete Continuous Mining System. Min. Cong. J., July 
1955, pp. 20-23. 

Illinois coal seam pillars are extracted by the Marietta miner (a modi- 
fied continuous miner) . Problems encountered and solutions are discussed. 



Stahl, R. W. Extracting Final Stump in Pillars and Pillar Lifts With Contin- 
uous Miners. BuMines RI 5631, [1960], 13 p. 

This article discusses various pillar extraction methods used in Pennsyl- 
vania with continuous mining machines. Common practices are delineated and 
safe practices are suggested. 



Stephenson, H. G. , C. W. Gregory, and W. J. Riva. Pillar Extraction in Thick 
Coal at Canmore, Alberta, on Gradients Between 5 and 30 Degrees. CIM Bull., 
November 19 72, pp. 52-62. 



172 



This article describes the methods used for pillar extraction in the 
Wilson seam at Canmore Mines, Alberta. Initially, a continuous miner/ 
shuttle car system was used. However, due to a thick, very gassy seam 
where roof conditions varied from good to appalling and a gradient ranging 
from 5 to 30 degrees, the initial system was abandoned and a slusher-loader 
system used instead, with excellent results. 



Stephenson, R. W. , and J. D. Rockaway. Pillar Support in Underground Coal 
Mines. Proc. 14th Ann. Eng. Geol. and Soils Eng. Symp. Boise, Idaho, 
1976, pp. 175-189. 

An analysis, based on a sample of 25 mines, of the strength and stability 
parameters of the strata underlying the coal in major coal basins of the 
United States was undertaken. Practices for the design of coal pillars in 
mines underlain by weak floors are recommended based on the analysis. 



Tien, J. C. J. Pros & Cons of Underground Ventilation Systems. Coal Min. 
and Proc, June 1978, pp. 110-134. 

The basic principles underlying the blowing and exhausting ventilation 
systems and their advantages and disadvantages are discussed. Recommenda- 
tions for improving ventilation are provided. 



Transactions of the Institution of Mining Engineers (London) . Transference 
of Roof Load, v. 108, 1949, pp. 490-504. 

The reduction of roof loads in narrow workings at depth by a yielding 
pillar technique is described. The application of the yielding pillar 
technique to room-and-pillar extraction is also discussed, and conclusions 
are drawn. 



Turnbull, L. A. , and A. L. Toenges. Mechanical Mining in Some Bituminous 
Coal Mines. Progress Report 5. Extraction of Pillars With Mechanized 
Equipment. BuMines IC 7527, 1949, 59 pp. 

This document is concerned primarily with the extraction of pillars and 
the mining problems incident to this phase of coal mining. The mining 
operations at several mines are described, which includes a general 
description of the mine and the mining method and pillar extraction 
procedure utilized. 



U.S. Bureau of Mines. Ground Control Aspects of Coal Mine Design: Proceed- 
ings Bureau of Mines Technology, BuMines IC 8630, 1974, 138 pp. 

This report includes an overview of the USBM approach to mine design and 
papers on problems associated with the design of panels and roof control. 



17 3 



U.S. Code of Federal Regulations. Title 30--Mineral Resources; Chapter 1 — 
Mining Enforcement and Safety Administration. Federal Register, July 1977, 
pp. 3-559. 

Regulations covering all aspects of mineral resources that are subject to 
enforcement by the Mining Enforcement and Safety Administration are 
presented. 



U.S. Mining Enforcement and Safety Administration. Roof and Rib Control: 
Programmed Instruction Workbook No. 3, NMHSA-CE-003, 1976. 

This publication is a programmed instruction workbook explaining roof and 
rib control. It includes a discussion on inspection and testing and acci- 
dent prevention. 



University of Utah. Site Characterization: 17th U.S. Symposium on Rock 
Mechanics Held at Snowbird, Utah, August 25-27, 1976. Utah Engineering 
Experiment Station, University of Utah, Salt Lake City, 1976. 

Pertinent papers cover subjects including selection of model and method 
of analyses for application of rock mechanics to engineering problems; 
design consideration for mining thick seams and seams lying in close 
proximity to one another; general principles of underground opening design 
in competent rock; and rock mechanics elements for coal mine design. 



Valeri, M. Pittsburgh-Seam Pillaring With Continuous Miners. Coal Age, 
March 1957, pp. 58-60. 

This article describes the retreat mining system used at Nemacolin, 
Pennsylvania. Mine conditions, roof control, and ventilation are among the 
topics covered. The system involves the use of conventional units and con- 
tinuous miners and an open-end pillaring method. 



The Mining Engineer. Ventilation Planning as a Prerequisite for Winning 
Higher Outputs. September 1971, pp. 796-811. 

Ventilation planning is discussed, including the economic consequences of 
inadequate ventilation capacity. Gas and dust control, underground booster 
fans, and firedamp drainage techniques are among the topics covered. 



Vorobjev, B. M. , and R. T. Deshmukh. Room-and-Pillar System. Advanced Coal 
Mining. Asia Publishing House, New York, v. 1, 1966. 

A description of room and pillar and block mining is provided, including 
the different types of rooms and necks and the different advancing/ 
retreating orders. 



17 4 



Wilson, J. W. , B. D. Singh, and S. Nakajima. Design Consideration for Mining 
Thick Seams and Seams Lying in Close Proximity to One Another. Unpublished 
paper. Available from the Consolidation Coal Company, Pittsburgh, Pennsyl- 
vania. 

This article inlcudes general principles of underground opening design in 
competent rock and a classification of rock. 



Younkins, J. A. Pillar Extraction With Continuous Machines. Min. Cong. J. , 
April 1952, pp. 36-39. 

The pillar extraction method employed with continuous machines at a 
Pennsylvania mine is described. 



Zachar, Frank R., Factors Influencing the Selection of Mining Systems. Min. 
Cong. J., October 1969, pp. 32-40. 

This article discusses the factors that need to be considered in select- 
ing a mining system (i.e., seam thickness, roof control and depth of cover, 
seam characteristics, market requirements, labor and supervision availabil- 
ity, return on capital investment, equipment, and ventilation requirements). 
Two different mining methods used in mining Pittsburgh seam coal are then 
compared. 



17 5 



APPENDIX. - RETREAT MINING PRACTICES 

This appendix contains tables summarizing the retreat mining practices in 
all but one of the MSHA districts. (District 1 is not included because it 
contains only anthracite coal mines. ) This appendix parallels the discus- 
sions in chapter 3 of this publication. 

A series of tables containing information summarized from the MSHA roof 
control plans are arranged in descending order of classification, by MSHA 
district. State (if necessary) , seam, and county. For example, in MSHA 
District 2, the first table is for the Brookville coal seam and entries are 
provided for each of the counties in which mining is conducted. The Upper 
Freeport Seam is listed first in the district because it has the greatest 
number of mines (31) . The next table contains data from the Pittsburgh Seam, 
which contains 30 mines. In this manner, the tables are arranged from seams 
with the most mines to those with the least mines. The counties are ordered 
depending upon the number of mines in the county. 

Within the tables, the information is arranged as follows: 

Column 1: County. The county in which the mines are located. 

Column 2: No. RCP. The number of roof control plans (RCP's) analyzed 
from the county noted in column 1. 

Column 3: Most Popular Process. Pillar extraction process most 
frequently practiced in the county. The following abbreviations are 
used: 

S&F - split and fender. 

P&W - pocket and wing. 

O.E. - open end. 

O.L. - outside lifts. 

P.O. - partial extraction using outside lifts. 

P.S. - partial extraction using splitting. 

No - more mines in the county do not practice pillar extraction than 
practice any of the individual pillar extraction processes. 

I.D. - insufficient data for categorizing any process as the most 
popular. 

Column 4: S&F. Number of mines in the county that have a plan on file 
for full pillar extraction by the split-and-fender process. 

Note: Roof control plans frequently contain pillar extraction plans 
for more than one process. It is entirely possible that a 
single roof control plan could contain plans for full pillar 



176 



extraction using each of the four basic processes and partial 
pillar extraction by both outside lifts and splitting. The 
result is that the entries in a row rarely add up to the total 
number of roof control plans analyzed in that county. 

Column 5: P&W. Number of mines in the county that have a plan on file 
for full pillar extraction using the pocket-and-wing process. 

Column 6: O.E. Number of mines in the county that have a plan on file 
for full pillar extraction using the open-end process. 

Column 7: O.L. Number of mines in the county that have a plan on file 
for full pillar extraction using the outside-lifts process. 

Column 8: Other. Number of mines in the county that have a plan on file 
for full pillar extraction using a process that does not fit into one of 
the four basic pillar extraction process classification categories. An 
entry in this column should be coupled with an explanatory entry in the 
"Other information" column. 

Column 9: O.L. Number of mines in the county that have a plan file for 
partial pillar extraction by removing outside-lifts. 

Column 10: Split. Number of mines in the county that have a plan on 
file for partial pillar extraction by taking splits through pillars. 

Column 11: Other. Number of mines in the county that have a plan on 
file for partial pillar extraction using a method that is not 
classifiable as outside lifts or splitting. An entry in this column 
should be coupled with an entry in the "Other information" column. 

Column 12: Do Not Pillar. Number of mines in the county that do not 
have plans for pillar extraction on file. 

Column 13: Other Information. Used for providing further elaboration 
when necessary. 

The purpose of presenting the tables that comprise the remainder of the 
appendix is to aid mine management in the selection of the retreat mining 
practice that will have the best chance of success in their mine. Careful 
consideration of the information in these tables is essential for any mine 
manager who is considering retreat mining. 



177 



DISTRICT 2 



SEAM Uppei 


■ Freeport 

Most 
No. Popular 
RCP Process 


OTHER NAI 

Full 
SSF PSW 


1ES 
















County 


Extraction Partial Extraction 
O.E. O.L. Other o.L. Split Other 


Do Not 

Pillar 


Other Information 


Indiana- 


10 


SSF 


8 


5 


I 

2 




1 


2 




3 




Allegheny 


6 


I.D. 


3 i 3 












2 




Armstrong 


6 


I.D. 


2 






2 




1 


1 




3 




Somerset 


5 


SSF 


3 ! 


i ' 








3 




i 
West- 
moreland 


3 


NO 






I 
i 










3 




Cambria 


1 


I.D. 


1 


1 










1 








TOTAL 


31 

























SEAM Pittsburgh 


Most 

Popular 
Process 


OTHER NAI 

Full 
SSF PSW 


1ES 










No. 
County RCP 


Extraction 

O.E. O.L. Other 


Partial Extraction 
O.L. Split Other 


DO Not 
Pillar 


Other Information 


Washington 


13 


PSW 


10 I 15 




1 

i 

1 


io ! 3 ! 


1 




Greene 


10 


PSW 


5 1 11 i 

1 1 1 


«i * i 


2 




Allegheny 


2 


PSW 


l| 2l 


1 
i 


1 i 






Fayette 


2 


PSW 


12! 


i ; I 






\ 
Irfest- 

Imoreland 


2 


SSF 


i i ! 
i l l ! 


i | I 






Indiana 


1 


No 


i 


i ■ . 


i 
i 


1 




TOTAL 


30 

















SEAM Lower Kittanning 


OTHER NAMES 










County 


Most 
No. Popular 
RCP Process 


Full Extraction 
SSF PSW O.E. O.L. Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


! 
Cabria 


7 


SSF 


I'll 

7 i i i -i : 
i i 




3 






1 [r.diana 


7 


No 


3 i : i i 






4 




Somerset 


6 


SSF 


3 ! J ; i 


; i 


2 




Armstrong 


3 


No 


! i 


1 : 

i j 


2 




Jefferson 


1 


No 


1 ! 


1 i 


1 




Clearfield 


1 


P.S. 


i i 1 | 

i i i 


: I '. 






1 TOTAL 


25 















178 



DISTRICT 2 



SEAM Lower Freeport 



OTHER NAMES 



No. 
County RCP 


Most 
Popular 
Process 


S&F 


Full 
PSW 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. split Other 


Do Not 
Pillar 


Other Information 


Indiana 


6 


SfiF 


3 


1 




1 






2 




2 




Cambria 


3 


1.0. 


3 


3 










2 








Jefferson 


4 


No 














1 




3 




Armstrong 


1 


I.D. 


1 






1 












TOTAL 


14 

























SEAM Upper Kittanning 



OTHER NAMES 



County 


No. 
RCP 


Most 
Popular 
Process 


SfiF 


Full 
P&W 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


00 Not 
Pillar 


Other Information 


Somerset 


7 


SfiF 


5 


1 




1 




2 


4 








Cambria 


4 


SfiF 


3 












2 








TOTAL 


11 

























SEAM Sewickley OTHER NAI 

Wost _ . , 

, Full 
No. Popular 

County RCP Process S&F P&W 


1ES 












Extraction Partial Extraction __■„.. 

Do Not 

O.E. O.L. Other O.L. Split Other Pillar Other Information 


; Greene 


6 


I.D. || 3 j 3 












h I 


1 

' TOTAL 


6 















SEAM Clarion 


Most 

Popular 
Process 


OTHER NAI 

Full 
S&F P&W 


■4ES Fulton 












No. 
County RCP 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Co Not 
Pillar 


Other Information 


I Indiana 


1 


SfiF 


1 

1 ! 

| 


1 i 

1 

i 1 


i 
1 








I 
Huntingdon 


1 


NO 


! : i 


• 


1 




I TOTAL 


2 



















179 






DISTRICT 2 



SEAM Middle Kittanning 


OTHER NAI 

Full 
S&f PSW 


4ES 
















Most 
No. Popular 

County RCP Process 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Clearfield 


1 


NO 


















1 




Canto ria 


1 


No 


















1 




TOTAL 


2 

























SEAM Brookville 



OTHER NAMES 



Most 
No. Popular 
County RCP Process S&F 


Full 
PSW 


Extraction Partial Extraction _ ., 

Do Not 

O.E. O.L. Other O.L. Split Other Pillar Other Information 


Centre 


1 


S&F ! 1 








1 




1 1 


TOTAL 


1 

















180 



DISTRICT 3 



SEAM Pittsburgh 



OTHER NAMES 



Most 
No. Popular Do Not 



Full Extraction 



Partial Extraction 



County 


RCP 


Process 


SSF 


PSW 


O.E. 


O.L. 


Other 


O.L. 


Spilt 


other 


Pillar 


otner information 


Harrison , 


10 


Ho 




2 


1 
i 

1 






3 




4 


!' 


Marshall 


7 


P.S. 






j 






6 




1 




Monongalia 


7 


PSW 




4 


! 






3 








> Marion 


6 


PSW 


1 


6 


i 










Barbour 


3 


No 






1 
i 






1 




2 


i 


Brooke 


3 


No 








1 




i I 

I 


2 


"1 

I 


Gilmer 


3 


SSF 

P.S. 

No 


1 












1 




1 


1 
i 

i 
■i 


TOTAL 


:- 

























SEAM Upper 


Freeport 

Most 
No. Popular 
RCP Process 


OTHER NAI 

Full 
SSF PSW 


flJS 
















County 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 

Pillar 


1 

1 

1 

Other Information 


Preston 


17 


P.S. 












1 


11 




5 




Garrett, 
Maryland 


3 


No 


















3 




Grant 


2 


O.L. 








2 














Barbour 


1 


NO 


















1 




Monongalia 


1 


NO 


















1 




Upshur 


1 


O.L. 








1 














TOTAL 


25 

r ~r - 

























SEAM Sewell 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular Do Not 

County RCP Process SSF PSW O.E. O.L. Other O.L. Split Other Pillar Other Information 



EH 



i Randolph 



17 



17 



I 



•Diagonal Cuts 



181 



DISTRICT 3 



SEAM Bedstone 


Most 
Popular 
Process 


OT 
S&F 


HER NAMES 
















No. 
County RCP 


Full Extraction 
P&W O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Monongalia 


6 


S&F 


3 


1 

1 








2 




1 




Barbour 


5 


SSF 


3 


j 




1 




1 




Lewis 


2 


O.L. 
No 




i ! » 










1 




Upshur 


1 


S&F 


1 


! 1 ! 




i 






j TOTAL 


_14 























SEAM Sewickley 


Most 
Popular 
Process 


OTHER NAMES 

Full Extract 
S&F P&W O.E. 
















No. 
County RCP 


Lon 
O.L. 


Other 


Partial Extraction . 
O.L. Split Other 


Do Not 
Pillar 


Other 


Information 


Monongalia 


13 


S&F 


! 

7 2 








1 


1 
j 


3 




Marion 


1 


NO 


1 
1 








1 




j TOTAL 


14 























SEAM Middle Kit tanning 



OTHER NAMES 



County 


No. 
RCP 


Most 
Popular 
Process 


S&F 


Full 
P&W 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other 


Information 


1 Upshur 


5 


No 


2 
















3 




! Braxton 

i 


1 


No 


















1 




1 Garrett, 
! Maryland 


1 


P.O. 












1 








i 


1 TOTAL 


7 



























SEAM Peerless 


MOSt 

Popular 
Process 


OTHER NAMES 












No. 
County RCP 


Full Extraction 
S&F P&W O.E. , O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other 


Information 


r 

: Randolph 


5 


No 


1 i ! 


l 


1 1 


1 ■ 






1 

! TOTAL 


5 

















182 





DISTRICT 3 

SEAM Lower Kittanninq 


OTHER NAMES 
















Most 
No. Popular 
County RCP Process 


Full 
S&F PSW 


Extraction 

O.E. O.L. 


Othei. . 


Partial Extraction 

O.L. Split Other 


Do Not 

Pillar 


■ i 
Other Information 








Barbour 


2 


NO 


















2 






Marion 


1 


P.O. 












1 








! 






TOTAL 


3 


















s 


CAM Baker 


stown 




OTHER NAM 

Full E 
S&F PSW 


£S 






Most 
No. Popular 
County RCP Process 


xtraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


i 

l 
I 

Other Information ] 






Grant 


2 


S&F |! 


2 


i 


! ! 


1 1 


1 


i 




i 


- -At 


2 


















SEAM Gilbert 




OTHER NA 

Full 
S&F PSW 


MES 






Most 
No. Popular 
County RCP Process 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 








1 
Randolpn 


2 


O.L. 
No 


i ' 1 


i ! ! 


1 






























SEAM Barton 




OTHER N; 

Full 
S&F PSW 


iMES 






Most 

No. Popular 
County RCP Process 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 








Garrett, 
MD 


1 


NO 






i 

i 


1 






TOTAL 


, 




















SEAM Clarion 





THER N 

Full 

PSW 


&MES 






Most 
No. Popular 
County RCP Process 


S&F 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
°-L. Split Other 


Do Not 

Pillar 


Other Information 


1 






i 

i Braxton 


1 


No 


i 1 i ; 1 > 








TOTAL 


1 









































183 



DISTRICT 3 

SEAM Hughs Ferry 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 

No. Popular -.--— . . . 0o NQt 

County TCP Process SfcF P6W O.E. O.L. Other .l. Split Other Pillar Other Information 



i r 



Randolph 



No 



UJ 



seam Upper Kittanning 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular uo noc 

County TCP Process S6F PSW O.E. O.L. Other O.L. Split Other Pillar Other Information \ 



Do Not 



1 



Barbour 



No 



m 



SEAM Welch 



OTHER NAMES 



Full Extraction 



Partial Extraction 



MOSt 

No. Popular " ""'" "' -•■•-■--• oo not 

County RCP Process S6F PSW O.E. O.L. Other O.L. Split Other Pillar Other Information 



i r 



-T 



Randolph 



No 



rzi 



184 



DISTRICT 4 



SEAM Sewell 




OTHER NA 

Full 

S4F P&W 


MES 
















No. 

County RCP 


Most 
Popular 
Process 


Extraction Partial Extraction 
O.E. O.L. Other o.L. Split Other 


DO Not 
Pillar 


Other Information 


Wyoming 


34 


No 


5 
















29 




McDowell 


30 


SiF 
NO 


15 


3 










3 > 
1 


15 




Nicholas 


27 


No 


5 






2 








22 




Webster 


17 


No 


1 












2 | 


14 




Fayette 


12 


No 


2 
















10 




Greenbriar 


6 


S&F 


3 












1 




2 




Raleigh 


2 


SSF 
No 


1 












1 

1 


1 




TOTAL 


12S 

























SEAM Eaal< 


1 

No. 

RCP 


Most 

Popular 
Process 


OTHER NA 

Full 
S&F P&W 


MES _» 


1 Gas . 


Mohawk , 


Bens Creek 








County 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
o.l. Split Other 


Do Not 

Pillar Other Information 


Logan 


23 


No 


3 










2 


3 




16 




Nicholas 


23 


No 


3 












1 




21 




.Wyoming 


17 


No 


3 






1 






1 




13 




i 
|Fayette 


9 


No 


2 




1 


1 






2 j 


7 




McDowell 


6 


NO 


1 












1 : 


4 




Kanawha 


3 


S&F 


2 












1 i 






Mingo 


3 


No 














1 i 


2 




Boone 


1 


I.D. 


1 


1 




1 






| 






Webster 


1 


P.S. 














1 
1 


1 




TOrAL 


86 

























185 





DISTRICT 4 

SEAM *2 Gas 


OTHER NAJ 

Full 
S6F P&W 


4ES Campbell Creek, Pond Creek, Upper War Eagle, Logan Eagle 


i 






M03t 
No. Popular 
County RCP Process 


Extraction Partial Extraction 
O.E. O..L. Other O.L. Split Other 


Do Not 

Pillar 


1 
Other Information 






Mingo 


31 


No 


6 












9 




17 






Raleigh 


13 


No 


S 




1 


1 






2 




8 






Boone 


10 


SSF 


5 


2 




1 






3 




3 






Kanawha 


7 


S&F 


5 


1 








1 




2 






Logan 


7 


NO 


1 


j 








2 




5 






Wyoming 


6 


P.S. 
No 


1 






1 






3 




3 






Fayette 


5 


S&F 


3 












1 ! 


2 






McDowell 


4 


NO 














! 
i 


4 






TOTAL 


S3 














SEAM #5 Block 




OT 
S&F 


HER NX 

Full 
PfiW 


MES Lower Kittanning 






Most 
No. Popular 
County RCP Process 


Extraction Partial Extraction 
O.E. O.L. Other O.L. Split Other 


DO Not 
Pillar 


Other Information 






Kanawha 


16 


P.S. 


7 












9 ! 
1 


5 






Nicholas 


16 


No 


2 












1 1 


13 






Boone 


12 


NO 












i 3 




9 


' 




Fayette 


9 


No 


1 










! x ! 


8 






Logan 


9 


S&F 

P.S. 

NO 


3 










! ' 

i 3 I 
1 1 


3 






Clay 


6 


No 












! ^ i 


4 






Raleigh 


1 


1.0. 


1 










I • ! 








TOTAL 


69 














SEAM Pocahontas 


#3 


OTHER NAJ 

Full 
S&F P&W 


4ES 






Most 
No. Popular 
County RCP Process 


Extraction Partial Extraction 
O.E. O.L. Other o.L. Split Other 


Do Not 
Pillar 


Other Information 






McDowell 


23 


S&F 


18 


10 


- 


4 






1 




2 






Raleigh 


22 


No 


6 


- 


1 


2 






2 ! 

; 


16 








Mercer 


12 


No 


3 


2 


- 


2 




! 

i 


9 








Wyoming 


11 


S&F 


9 


6 


1 


2 j 




2 








Fayette 


1 


No 




i 




i 


1 








TOTAL 


69 





































186 



DISTRICT 4 



SEAM Cedj 


r Grove 

Most 
No. Popular 
RCP Process 


OTHER NAI 

Full 
S&F P&W 


1ES Thacker 














County 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. split Other 


DO Not 
Pillar 


Other Information 


Logan 


33 


No 


8 






1 




3 


10 




15 




Mingo 


14 


NO 


1 






1 










13 




Boone 


11 


NO 


3 


2 










3 




7 




Wyoming 


7 


P.S. 














5 j 


2 




TOTAL 


65 

























SEAM Red Ash 



OTHER NAMES Douglass, Raven Red Ash 



County 


No. 

RCP 


Most 

Popular 
Process 


S&F 


Full 

PSW 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


I 
Other Information 


McDowell 


46 


No 


4 












4 




38 




Wyoming 


8 


No 


















8 




'total 


54 

























SEAM Winifrede 


Most 
Popular 
Process 


OTHER NAI 

Full 
S&F P&W 


1ES Dorothy_ 














No. 

County RCP 


Extraction Partial Extraction 
O.E. O.L. Other O.L. Split Other 


Do Not 
Pillar 


Other Information 


Boone 


18 


No 


3 


2 










3 




13 




Logan 


18 


No 


1 










1 


1 




16 




Kanawha 


8 


No 


1 








1 


2 




6 




Mingo 


3 


NO 








': 




1 




2 




Wyoming 


2 


P.S. 
No 


1 












i 
1 i 


1 




Fayette 


1 


I.D. 


1 




1 








1 








Nicholas 


1 


No 














1 
i 


1 




Raleigh 


1 


S&F 


1 












| 






Wayne 


1 


No 
















1 




[TOTAL 


53 

























187 



DISTRICT 4 

SEAM Beckiey 


Most 
Popular 
Process 


OTHER NAMES Pocahontas #12, War Creek 












No. 

County RCP 


Full Extraction Partial Extraction 
S&F PSW O.E. O.L. Other O.L. Split Other 


Do Not 
Pillar 


Other Information 








Raleigh 


22 


No 


4 


1 










1 




18 






Wyoming 


11 


No 


3 












3 




7 






McDowell 


a 


SSF 


6 












1 




1 






Greenbriar 


2 


No 


















2 






Mercer 


1 


S&F 


1 












1 








Nicholas 


1 


No 




i 














1 






TOTAL 


45 


#11 

MOSt 

Popular 
Process 














SEAM Rocahontas 

No. 
County RCP 


OTHER NAI 

Full 
SSF PSW 


4ES Firecreek 






Extraction Partial Extraction 
O.E. O.L. Other o.L. Split Other 


Do Not 
Pillar 


Other Information 








McDowell 


21 


No 


6 


- 


1 


2 






4 




13 






Fayette 


8 


No 


1 
















7 






Raleigh 


8 


No 


















8 






Greenbriar 


2 


No 


















2 






Mercer 


1 


O.E. 






1 








1 












TOTAL 


41 


ewiston 

Most 
Popular 
Process 














SEAM Stockton-I 

No. 

County RCP 


OTHER NA 

Full 
SSF PSW 


MES Lewiston-Belraont 






Extraction Partial Extraction 
O.E. O.L. Other o.L. Split Other 


DO Not 
Pillar 


Other Information 








Boone 


16 


No 


2 












7 




8 






Logan 


8 


No 














3 




5 






Kanawha 


8 


NO 














1 




7 






Fayette 


3 


No 














1 




2 






McDowell 


1 


No 














1 


1 






Raleigh 


1 


NO 














1 








TOTAL 


37 





































188 



DISTRICT 4 



SEAM Pocahontas 


»6 

Most 

Popular 
Process 


OTHER NAI 

Full 
SfcF PfiW 


1ES 
















No. 

County RCP 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.E. Split Other 


DO Not 
Pillar 


■ 
Other Information 


Wyoming 


16 


No 


4 


1 










2 




11 




Greenbriai 


7 


No 


1 












1 




5 




McDowell 


5 


SSF 


3 


2 














1 




1 

1 Summers 


4 


NO 


















4 




Mercer 


1 


I.D. 














1 








Raleigh 


1 


NO 


















1 




TOTAL 


34 

























SEAM Gilbert 


Most 
Popular 
Process 


OTHER NAI 

Full 
SSF PfiW 


4ES McGowan 














No. 

County RCP 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Wyoming 


24 


No 


10 
















14 




McDowell 


4 


No 


1 
















3 




Nicholas 


2 


No 


















2 




Fayette 


1 


NO 


















1 




1 
1 

i TOTAL 


31 

























SEAM Alma 



OTHER NAMES Warfield 



County 


No. 
RCP 


Most 
Popular 
Process 


S&F 


Full 
PfiW 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Mingo 


25 


No 


3 


1 




1 






4 




17 




Logan 


4 


No 


















4 




McDowell 


1 


No 


















1 




TOTAL 


30 

























189 



DISTRICT 4 



SEAM Coalburq 


Most 
Popular 
Process 


OTHER NAI 

Full 
SSF P&W 


1ES 
















No. 
County RCP 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.E. O.L. Other 


Do Not 
Pillar 


Other Information 


Kanawha 


11 


No 


2 




1 








2 




a 




Logan 


7 


No 














2 




5 




Mingo 


7 


No 


















7 




Boone 


3 


No 


















3 




Clay 


1 


No 


















1 




TOTAL 


29 























SEAM Chilton 


Most 
Popular 
Process 


OTHER NA 

Full 
SSF PSW 


MES Taylor 














No. 
County RCP 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 

Pillar 


Other Information 


Logan 


29 


No 


'• 








1 ■ 


5 


1 »l 


! TOTAL 
L 


29 

























SEAM Pocahontas 


#4 

Most 
Popular 
Process 


OTHER NA 

Full 
SSF PfiW 


NES 
















NO. 

County RCP 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


McDowell 


15 


S£F 
P&W 


11 


11 


1 


2 






2 




4 




Raleigh 


8 


No 


1 




1 












7 




Wyoming 


6 


No 


2 












1 




3 




1 TOTAL 


29 

























SEAM Lower Ceda 


r Grove 


OTHER NAI 

Full 
S&F PSW 


1ES 
















County 


NO. 
RCP 


Most 
Popular 
Process 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Logan 


14 


No 












1 


2 




11 




Mingo 


11 


No 


4 


2 








1 


2 


. 


5 




Boone 


1 


NO 














i 


1 




Wyoming 


1 


P.S. 














1 






1 

| TOTAL 


27 

























190 



DISTRICT 4 



SEAM Pe «r 


less 




OTHER NA 
Full 

sir Ptw 


HES 
















County 


No. 

RCP 


Host 
Popular 
Process 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Nicholas 


8 


No 














1 








Webster 


6 


No 


1 




















Boon* 


5 


NO 


1 












1 








Kanawha 


3 


No 






















Raleigh 


2 


su- 
ite 


1 




















TOTAL 


24 

























SEAM Powellton 


MOSt 
Popular 
Process 


OTHER NAi 

Full 

SLF PtW 


MES 
















No. 
County RCP 


Extraction Partial Extraction 
O.E. O.L. Other O.L. Split Other 


Do Not 

Pillar 


Other Information 


Logan 


S 


P.S. 














3 




2 




Boone 


3 


1.0. 


1 


1 














2 




Fayette 


3 


NO 












1 






2 




Kanawha 


3 


NO 


1 












1 




2 




Wyoming 


2 


SiF 
P.S. 


1 












1 








Raleigh 


1 


P.S. 














1 








TOTAL 


17 

























191 



DISTRICT 4 



SEAM Little Eagle 



OTHER NAMES 



County 


No. 
RCP 


Most 
Popular 
Process 


S&F 


Full 
PSW 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Wyoming 


6 


No 


1 












1 




4 




Fayette 


3 


No 


















3 




McDowell 


1 


No 


















1 




Nicholas 


1 


No 


















1 




TOTAL 


11 























SEAM Pocahontas 


#10 

Most 
Popular 
Process 


OTHER NAI 

Full 
St? PGW 


>1ES 
















No. 
County RCP 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


McDowell 


10 


SfcF 


• 








1 




1 • 




TOTAL 


10 























SEAM Welch 



OTHER NAMES Smith 



Full Extraction 



Partial Extraction 



Most 
No. Popular Do Not 

County RCP Process S&F P&W o.E. O.L. Other o.L. Split Other Pillar Other Information 



McDowell 



10 



No 



in 



10 



SEAM Pnr.^hnprAg 


«* 


OTHER NAI 

Full 
S&F P&W 


1ES 














No. 

County RCP 


MOSt 

Popular 
Process 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


McDowell 


6 


S&F 

No 


3 


2 












3 




Raleigh 


3 


NO 


| 
1 










I 


3 




TOTAL 


9 























192 



DISTRICT 4 



SEAM Pocahontas 


#9 

Most 

Popular 
Process 


OTHER NAI 

Full 
SIT PSW 


1£S 












, , 


No. 
County RCP 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


McDowell 


9 


SSF 


5 


I 






1 




4 




TOTAL 


9 





















SEAM Hern; 


ihaw 

No. 

RCP 


Most 

Popular 
Process 


OTHER NAI 

Full 
SSF PSW 


ffiS 








• 








County 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Boone 


4 


SSF 
O.L. 


2 






2 






1 




1 ' 




Kanawha 


2 


SSF 


1 












1 




1 




Raleigh 


1 


SSF 


1 












1 








TOTAL 


7 

























SEAM . , Lower Wax... 

No. 
County RCP 


Eagle 

MOSt 
Popular 
Process 


OTHER NAI 

Full 
SSF PSW 


•as 
















Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


McDowell 


4 


NO 














1 




3 




Mingo 


1 


I.D. 


1 










1 


1 








Wyoming 


1 


No 


















1 




TOTAL 


6 

























SEAM Upper Eagle 



OTHER NAMES Hatewan 



Full Extraction 



Partial Extraction 



Most 
No. Popular Do Not 

County RCP Process SSF PSW O.E. O.L. Other O.L. Split Other Pillar Other Information 



Raleigh 



Logan 



S&F 



Wyoming 



193 



DISTRICT 4 



SEAM Uppe 


c Kictanning 

Most 
No. Popular 
RCP Process 


OTHER NAI 

Full 

SiF PiW 


1ES 
















County 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Nicholas 


5 


No 


















5 




Clay 


1 


No 


















1 




TOTAL 


6 

























SEAM Bradshaw 



OTHER NAMES Hughes Ferry. laeqer 

Full Extraction Partial Extraction 



Most 
No. Popular 
County RCP Process SfcF P&W O.E. O.L. Other O.L. Split Other Pillar Other Information 



Do Not 



McDowell 



S&F 



m 



SEAM Lowei 


■ Freeport 

Most 
No. Popular 
RCP Process 


OTHER NAI 

Full 
S&F P&W 


HES Freeport 














County 


Extraction 
O.E, O.L. Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Boone 


3 


S&F 


2 
















1 




Mingo 


1 


NO 


















1 




TOTAL 


4 

























SEAM Williamson 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular Do Not 

County RCP Process S6F Psw o.e. O.L. Other o.l. Split Other Pillar Other Information I 



Logan 


2 


S&F 
NO 


1 
















1 


™1 

1 

J 


Mingo 


1 


No 


















1 


j 


TOTAL 


3 

























194 



DISTRICT 4 



SEAM Pocahontas »2 



OTHER NAMES 



County 


No. 
RCP 


Most 
Popular 
Process 


Sif 


Full 
PSW 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


McDowell 


1 


No 


















1 




Mercer 


1 


No 


















1 




TOTAL 


2 

























SEAM Pittsburgh 8 



OTHER NAMES Raymond 



Full Extraction 



Partial Extraction 



Most 
No. Popular Do Not 

County RCP Process S&F PSW O.E. O.L. Other o.L. Split Other Pillar Other Information 



m 



SEAM Glen Alum 



OTHER NAMES 



County 


No. 
RCP 


Most 
Popular 
Process 


S&F 


Full 
PSW 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 

Pillar 


Other Information 


Fayette 


1 


1 








1 




1 « 1 


TOTAL 


1 

























195 



DISTRICT 5 



SEAM Blair 



OTHER NAMES Eagle, Bens Creek, Norton #1 



County 


No. 

RCP 


Most 
Popular 
Process 


S&F 


Full 

PSW 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Buchanan 


184 


No 


5 










3 


19 




157 




Dickenson 


4 


No 














1 




3 




Wise 


2 


No 


















2 




TOTAL 


190 

























SEAM Widow Kennedy 


OTHER NAI 

Full 

StF P&W 


IBS Kennedy 














Most 
No. Popular 
County RCP Process 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Buchanan 


92 


No 


9 










3 


8 




63 




Russell 


27 


No 


1 












4 




22 




Dickenson 


13 


NO 


















13 




Scott 


1 


No 


















1 




TOTAL 


133 

























SEAM Splashdam 



OTHER NAMES 



County 


No. 
RCP 


Most 
Popular 
Process 


SSF 


Full 
PCW 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Buchanan 


95 


No 


1 




1 






3 


5 




85 




Dickenson 


17 


No 














2 




15 




Wise 


1 


No 


















1 




TOTAL 


113 

























SEAM Banner 


Most 
Popular 
Process 


OTHER NAI 

Full 
S&F PSW 


1ES 
















No. 
County RCP 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Dickenson 


45 


No 


8 




• 






1 


6 




31 




Wise 


18 


No 


2 










1 


2 




13 




Buchanan 


11 


NO 


2 












1 




9 




Russel 


9 


No 


















9 




TOTAL 


83 




• 





















196 



DISTRICT 5 



SEAN Jawbone 


Most 
Popular 

Process 


OTHER NA 

Full 
S&F PfcW 


MES Tiller 














No. 

County RCP 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Buchanan 


65 


No 


8 










1 


10 




46 




Wise 


6 


No 


















6 




Dickenson 


4 


No 


















4 




Tazewell 


4 


NO 


1 
















3 




Russell 


3 


ssr 


2 












1 




1 




TOTAL 


82 

























SEAM Red Ash 



OTHER NAMES Imboden, Raven 



County 


No. 

RCP 


MOSt 
Popular 
Process 


SSF 


Full 
PSW 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 

Pillar 


Other Information 


Buchanan 


53 


No 


3 




2 






2 


3 




44 




Di etc en s on 


12 


No 


1 
















11 




Russell 


6 


No 














1 




5 




Tazewell 


4 


No 


1 












1 




3 




wise 


4 


S&F 


3 


1 


















TOTAL 


79 

























SEAM Hagy 



OTHER NAMES Norton 



County 


No. 

RCP 


Most 
Popular 
Process 


S&F 


Full 
PSH 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 

Pillar 


Other Information 


Buchanan 


64 


No 


4 






1 




1 


13 




48 




Wise 


11 


No 


















11 




Lee 


2 


No 


















2 




TOTAL 


77 

























SEAM Glamorgan 



OTHER NAMES Dorchester, Cedar 



Full Extraction 



Partial Extraction 



Most 
No. Popular »-.•—-- „„.,..,._... Do Not 

County RCP Process S6F P&W O.E. O.L. Other O.L. Split Other Pillar Other Information 



Buchanan 


39 


No 


1 










3 


10 




27 


j 


Dickenson 


9 


NO 


















9 


! 


Wise 


9 


No 


1 
















8 


i 


1 

| TOTAL 


57 

























197 



DISTRICT 5 

SEAM Mason 



OTHER NAMES Taggart 



County 


No. 

RCP 


Most. 
Popular 
Process 


SSF 


Full 
PSW 


Extraction 

O.E, O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Lee 


30 


No 


1 










1 


1 




29 




Wise 


19 


SSF 


9 










1 


2 


1 


8 




TOTAL 


49 

























SEAM Clintwood 



OTHER NAMES Feds Creek, Matewan 



County 


No. 
RCP 


Most 
Popular 
Process 


SSF 


Full 
PSW 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Buchanan 


15 


No 


1 










1 


5 




9 




Dickenson 


12 


No 


















12 




Wise 


12 


No 


















12 




i 

| TOTAL 


39 

























SEAM Horsepen 



OTHER NAMES Seaboard 



Full Extraction 



Partial Extraction 



Most 
No. Popular Do Not 

County RCP Process SSF PSW O.E. O.L. Other o.L. Split Other Pillar Other Information j 



EH 



Tazewell 



19 



19 



SEAM Boiling 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular .--.-■ ^ NQt 

County RCP Process S&F PSW O.E. O.L. Other O.L. Split Other Pillar Other Information 



m 



12 



Bacsoas 



OTHER NAMES Morris. Smith 



Full Extraction 



Partial Extraction 



Most 

lull LAtiackiun raj.ixa.L lai.ioi,i.ijii 

No. Popular Do Not 

County RCP Process SSF PSW O.E. O.L. Other O.L. Split Other Pillar Other Information 



Wise 


11 


NO 2 






2 


1 


1 


1 


1 


- 1 i 


i 

j TOTAL 


11 


1 



















198 



DISTRICT 5 





Most 
Popular 
Process 


OTHER NAI 

Full 
S6F P&W 


1ES 
















No. 
County RCP 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Buchanan 


5 


No 


1 


1 










1 




4 




Tazewell 


5 


No 


' 1 












1 




3 




TOTAL 


10 























SEAM Kelly 



OTHER NAMES Alma. Upoer Elkhom. Wariield 



Full Extraction 



Partial Extraction 



Most 
No. Popular Do Not 

County RCP Process SSF PSW O.E. O.L. Other O.L. Split Other Pillar Other Information 



No 



m 



SEAM Cove Creek 


Most 

Popular 
Process 


OTHER NAI 

Full 

S&F PSW 


■ffiS 
















No. 
County RCP 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


i 

1 
Other Information 


Scott 


3 


No 










1 




1 ■ 1 


TOTAL 


3 

























SEAM Phillips 


Most 
Popular 
Process 


OTHER NA 

Full 
SSF PtW 


1ES 
















No. 

County RCP 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Tazewell 


1 


No 


















1 




Wise 


1 


No 


















1 




TOTAL 


2 

























SEAM Lyons 


Most 

Popular 
Process 


OTHER NAI 

Full 
SSF PSW 


^ s Fraley 














No. 

County RCP 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Wise 


1 


•- 11 




| 


1 


1 


1 1 


TOTAL 


1 





















199 



DISTRICT 6 



SEAM Elkhc 


rn <3 




CITHER NAI 

Full 
S&F PSW 


4ES 
















No. 
County RCP 


Most 
Popular 
Process 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Pike 


58 


NO 












1 


5 


52 




Letcher 


53 


NO 


7 












5 




43 




Floyd 


46 


No 


1 












9 i 


36 




Johnson 


9 


No 






1 
i 




1 ! 


8 




TOTAL 


166 

























SEAM Elkhorn #2 




OTHER NA1 

Full 
S6F PSW 


1E5 


















Ho. 
County RCP 


Most 
Popular 
Process 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other 


Information 


Pike 


105 


NO 


• i ! 


^ 




16 




86 




Floyd 


32 


NO 








5 




27 




Letcher 


5 


NO 


i 


I I 


i 
I 




4 


1 


1 

! TOTAL 


142 

























SEAM Hazard *-l 


MOSt 

Popular 
Process 


OT 
S&F 


HER NAJ 

Full 
PSW 


1ES 












No. 

County RCP 


Extraction Partial Extraction 
O.E. O.L. Other O.L. Split Other 


Do Not 
Pillar 


Other Information 


Letcher 


68 


NO 


a ! 


! 




6 




60 




Floyd 


25 


NO 


! 


i 

i 




i 

! 4 ' 


21 




jpike 


16 


No 


2 


i 




4 ; 


10 




(lartin 


14 


NO 


> 






i 6 ; 


7 




Kigocf in 


2 


NO 


i ' ! 


i 


2 




Johnson 


1 


No 


! ! i ! 
i 


; 


1 




i 

! TOTAL 


126 





















200 



DISTRICT 6 



SEAM Lower Elkhorn 


OTHER NA 

Full 
S&F P&W 


HES 
















Most 

No. Popular 
County RCP Process 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Pike 


113 


No 


10 


1 










25 




80 




Letcher 


5 


No 






i 








5 




Martin 


2 


No 






1 






| 


2 




TOTAL 


120 

























SEAM tlkhorn Kl 


Most 
Popular 
Process 


OTHER NAI 

Full 
S&F P&w 


1ES Al 


ma 














No. 
County RCP 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 

Pillar 


Other Information 


Pike 


80 


No 


5 












9 




66 




Floyd 


13 


Mo 


















13 




Martin 


I 


P.S. 




' 








1 ! 






TOTAL 


94 

























SEAM Winifrede 


Most 
Popular 
Process 


OTHER NAI 

Full 
S&F P&W 


1ES 














No. 
County RCP 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


DO Not 
Pillar 


Other Information 


Pike 


33 


No 














8 ' 


25 




Magoffin 


14 


No 














"" ! 


14 




Floyd 


7 


Mo 






j 




2 ! 


5 




Letcher 


6 


No 








1 




2 


A 




Martin 


2 


NO 








1 

i 


: 

1 ; 


2 




Johnson 


1 


No 








j 


1 ! 

! ! 


1 




TOTAL 


62 























201 



DISTRICT 6 



SEAM Broji 


No. 
RCP 


Most 
Popular 
Process 


OTHER NM 

Full 
Sfcf PSW 












County 


Extraction Partial Extraction 
O.E. O.L. Other o.l. Split Other 


Do Not 
Pillar 


Other Information 


Pike 


26 


No 


2 












6 




18 




Floyd 


16 


P.S. 












2 


8 




6 




Martin 


6 


1.0. 


' 3 












1 

3 ! 


3 




Johnson 


5 


No 














1 


5 




Magoffin 


2 


NO 






' 1 
i 




i 


2 




TOTAL 


55 























SEAM Clintwood 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular ' " -—.,-. ^ (Jot 

County RCP Process SSF PSW o.E. O.L. Other o.L. Split Other Pillar Other Information 



46 



IS 



rzi 



46 



SEAM Amburgy 

No. 

County RCP 


Most 

Popular 
Process 


OTHER NAI 

Full 
SfcF P&W 


1ES 
















Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Floyd 


8 


No 


















8 




Pike 


7 


No 














l ; 


6 




Letcher 


2 


NO 












| 

i ' 


2 




TOTAL 


17 

























SEAM whitesbun 


Most 

Popular 
Process 


or 

SfcF 


HER NAMES 














No. 

County RCP 


Full Extraction 
P4W O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Letcher 


14 


No 




1 
1 








1 

i 


14 




Pike 


2 


NO 




1 

I 








i 


2 




Floyd 


1 


NO 




1 
i 








1 


1 




j TOTAL 


17 





















202 



DISTRICT 6 



SEAM Eagle 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular Do Not 

County RCP Process SfiF PfiW O.E. O.L. Other O.L. Split Other Pillar Other Information 



Pike 



15 



No 



m 



15 



SEAM Splashdam 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular Do Not 

County RCP Process SfiF PfiW o.E. O.L. Other o.L. Split Other Pillar Other Information 



Pike 



11 



Lin 



TOTAL 



11 



SEAM Haov 


No. 

RCP 


Most 
Popular 
Process 


OTHER NAI 

Full 
SfiF PfiW 


1ES 
















County 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Pike 


10 


No . 1 








1 




| , | 


TOTAL 


10 

























SEAM Hazard *6 and »7 



OTHER NAMES 



County 


No. 

RCP 


Most 
Popular 
Process 


SfiF 


Full 
PfiW 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Magoffin 


1 


NO 


















1 




Pike 


2 


NO 


















2 




TOTAL 


3 

























SEAM Skyline OTHER NAI 

*" Full 
No. Popular 

County RCP Process S&F PfiW 


1ES 






Extraction Partial Extraction _ „ „ 

Do Not 

O.E. O.L. Other o.L. Split Other Pillar Other Information 


Magoffin 


2 


- 1 ! 






II ! 1 > 1 


TOTAL 


2 











203 



DISTRICT 6 



SEAM no. 5 Block 



OTHER NAMES 



Most 
No. Popular 



Full Extraction 



Partial Extraction 



Do Not 



County RCP Process S&F P&W o.E. O.L. Other o.L. Split Other Pillar Other Information 



TOTAL 



a 



204 



DISTRICT 7— Alabama 



SEAM Blue 


Creek 


OTHER NAMES Richland 


, Upper 


:iiff 










County 


No. 
RCP 


MOSt 

Popular 
Process 


Full Extraction 
SSF PSW O.E. O.L. 


Other 


Partial Extraction 
0. L. Split Other 


Do Not 
Pillar 


Other Information 


Jefferson 


3 


No 


.1-1.1 

j 


1 






2 




iTusca loose 


3 


No 










3 




| Cherokee 


1 


No 




! i 






1 


1 




1 
1 
TOTAL 


7 





















SEAM Mary 
County 


Lee 

No. 
RCP 


Most 

Popular 
Process 


OTHER NAI 

Full 

SSF PSW 


>IES Sewanee, 


Sewell 








Extraction 
O.E. O.L. 


Other 


Partial Extraction 
0. L. Split Other 


Do Not 

Pillar 


Other Information 


1 

iJef ferson 


4 


No 


1 

i 




! 


1 I 

1 i 


3 




; Walker 


3 


I.D. 


i 1 ■ 1 ! 

1 ! 


I 

! 1 


i ; 


2 




'TOTAL 





















SEAM Black Creek 

Most 
No. Popular 
County RCP Process 


OTHER NAMES wilder. Bat;t;e Creek 








Full Extraction Partial Extraction 

DO Not 
SSF PSW O.E. O.L. Other O.L. Split Other Pillar Other Inforrution 


; Marion 


2 


NO 


I'll 


1 ! 


2 




jBlount 


1 


No 


1 ! I 1 




i 


1 




j Jackson 


1 


No 


1 '' [ ! 




! 


1 




Jefferson 
1 , _,. 


1 


No 


! : i ! 


i 


1 




1 
1 
TOTAL 


S 















SEAM Pratt 




OTHER NAMES 








. ftos , t Full Extraction Partial Extraction 
No. Popular D° Not 
County RCP Process S&F PSW O.E. O.L. Other O.L. Split Other Pillar Other Infomaticn 


] Jefferson 


3 


O.E. 
Other 


: ! i 

! i 2 ; j 1 


i 1 

j 1 

1 

1 i 






l Fayette 


1 


SSF 


i ! ! ! ■ ! 

1 ! 1 1 


1 
1 i 






: TOTAL 


4 













205 



DISTRICT 7 — Alabama 



SEAM America 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular " Do Not 

County RCP Process S&F PSW O.E. O.L. Other o. L. Split Other Pillar Other Information 



No 
See Note 



I 



•Diagonal cuts through 
pillar 



• Diagonal cuts through 
pillar 



SEAM Gholson OTHER NAJ 

Most _ ,, 
Full- 
No. Popular 

County RCP Process S&F P&W 


<4ES Mammoth 






Extraction Partial Extraction _ „ 

Do Not 

O.E. O.L. Other O.L. Split Other Pillar Other Information 


Shelby 


2 




I 


L 


i 




! 1 » 1 


j 

| TOTAL 


2 















206 



DISTRICT 7— Kentucky 



SEAM Hazard #4 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular Oo Not 

County RCP Process SSF PSW O.E. O.L. Other O.L. Split Other Pillar Other Information 



Leslie 



60 



No 



54 



jKno 



10 



Bell 



I 1 



Clay 



Kno 



TOTAL 



SEAM Elkhc 


rn *3 

No. 
RCP 


Most 
Popular 
Process 


OTHER NAI 

Full 
SSF PSW 


HES Darby, Kelllka, Stearns »3, Lower Mason 


Rim 




County 


Extraction 

O.E. O.L. Other 


Partial Extraction 
O.L. Split Other 


Oo Not 

Pillar 


Other Information 


1 
fiarlao 


68 


No 


■ !■ 


, ; ! 


! > ! 


62 




Knotc 


39 


No 


i | i ! | 


! i 


37 




Knox 


1 


No 


! ! 1 ! 




1 




M;Creary 


1 


No 


! i 1 

• ; 


i ! 


1 




Perry 


1 


No 


1 i 1 1 


I 


\ 




pCTAL 


110 















iEAM Elkhorn »I 



Most 

No. Popular 



OTHER NAMES Hance, Blue Gen, Jellico Harlan, Lower Elkhorn 



Full Extraction 



Partial Extraction 



Do Not 
County RCP Process S&F PSW O.E. O.L. Other O.L. Split Other Pillar Other Information 









• . 


* 






, 


Harlan 


59 


No 


1 i ! 1 
1 1 ; 


I 

3 1 


1 

7 ' 7 


46 






Knox 


22 


No 


i 
I : 


; ; 


22 




Kr.ott 


9 


No 


1 j 


| ; 


8 




i 

Sell 


7 


No 


i . . i 

i ; ■ : ! i i 


| 


6 




I 

jWhicley 


4 


No 


'■ ' ! ! 
i 




4 






[McGreary 


1 


I.D. 


! 1 ! i 

1 i 


l : 
i 


1 


i 




i 

(total 


102 















207 



DISTRICT 7— Kentucky 



SEAM Uppei 


Mason 

Most 
No. Popular 
RCP Process 


OTHER NAI 

Full 
SfiF PSW 


>1ES Creech, Mason, Amburgy, 


D 








County 


Extraction Partial Extraction 
O.E. O.L. Other o.L. Split Other 


Do Not 
Pillar 


Other Information 


Marian 


62 


No 












5 


11 


9 


47 




Bell 


12 


No 














2 


2 


10 




TOTAL 


74 

























SEAM Hazard No. 


5 S 5A 


OTHER NAJ 

Full 
S&F PSW 


^ES Haddix, 


Smith, Hignite 








No. 
County RCP 


Most 
Popular 
Process 


Extraction 
O.E. O.L. 


Partial Extraction 
Other o.L. Split Other 


Do Not 
Pillar 


Other Information 


Leslie 


14 


NO 


1 




! ! 




, ! 


12 




Perry 


14 


HO 


1 






; 




i 
2 ! 


12 




Sell 


11 


No 




' i 


1 


1 
1 , 2 J 


3 




Harlan 


10 


NO 




1 
i 


1 


3 ! ^ J 


7 




Breathitt 


3 


No 




1 i 
1 


! ; 
i 


3 




Knott 


2 


NO 




i i 


! 1 


2 




^lay 


1 


No 




! i 

1 




i 1 
1 


1 




TOTAL 


55 























SEAM Hazard No. 


6 & 7 

Most 
Popular 
Process 


OTHER NAJ 

Full 
SfiF P&W 


*ES 
















No. 
County RCP 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Knott 


22 


No 


1 


1 
1 








1 




20 




Perry 


18 


No 


2 












4 




13 




Breathitt 


3 


NO 


















3 




Harlan 


3 


No 


1 


1 

! 






1 i 

1 


2 




TOTAL 


46 

























208 



DISTRICT 7 — Kentucky 



SEAM Hors< 


i Creek 

Most 
No, Popular 
RCP Process 


OTHER NAI 

Full 
SSF PiW 


1ES Glen Mary, Lily 












County 


Extraction 

O.E. O.L. Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Clay 


21 


No 


1 

1 

1 














21 




Laurel 


4 


No 


I 
i 










j 


4 




Leslie 


1 


No 


1 
1 










I 
I 


1 




Pulaski 


1 


NO 






I 

i 










1 




Rockcastle 


1 


NO 






I 




: 

I 


1 




1 

[total 


28 

























SEAM Elkhorn #2 




OTHER NAI 

Full 
S&F PSW 


4£S Leonard, 


Stearns 


«2 










County 


No. 
RCP 


Most 
Popular 
Process 


Extraction 
O.E. O.L. 


Partial Extraction 
Other o.L. Split Other 


Do Not 
Pillar 


Other Information 


Bell 


6 


No 


















6 




Knott 


6 


No 


















6 




Wayne 


2 


No 


















2 




Jackson 


1 


No 


















1 




! 

McGreary 


1 


P.S. 














1 









Pulaski 


1 


I.D. 






j 




1 


1 






1 


TOTAL 


17 

























SEAM Hazard #9 



OTHER NAMES Hindman 



County 


NO. 

RCP 


Most 
Popular 
Process 


SSF 


Full 
PSW 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Harlan 


4 


No 


















4 




Perry 


4 


S6F 
No 


2 1 










1 




2 




Knott 


2 


NO 












j 


2 




Leslie 


2 


I.D. 


1 
i i 




1 


1 


1 




TOTAL 


12 

























209 



DISTRICT 7 — Kentucky 



SEAM Hazard #8 


Most 

Popular 
Process 


OTHER NAJ 

Full 
S&F PSW 


4ES 
















No. 
County RCP 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Leslie 


2 


No 


















2 




Harlan 


1 


No 


















1 




:Perry 


1 


No 


















1 




i 
TOTAL 


4 

























SEAM Whitesburg 



OTHER NAMES 



County 


NO. 

RCP 


Most 
Popular 
Process 


S&F 


Full 
PEW 


Extraction 
O.E. O.L. 


Partial Extraction 
Other o.L. Split ' Other 


Do Not 
Pillar 


Other Information 


Clay 


1 


P.S. 










1 


1 








Harlan 


2 


NO 










1 

1 






2 




TOTAL 


3 























SEAM Hi 9h 


Splint 

Most 
No. Popular 
RCP Process 


OTHER NAJ 

Full 
S&F P&M 


HES NO 


. S Block, Lower Kit tanning 








County 


Extraction Partial Extraction 
O.E. O.L. Other O.L. Split Other 


Do Not 
Pillar 


Other Information 


Breathitt 
1 


1 


No 


















1 




Harlan 


1 


S&F 


1 


















TOTAL 


2 

























SEAM Skyline 

No. 
County RCP 


Most 
Popular 
Process 


OTHER NAI 

Full 
S&F PtW 


MES 












Extraction 

O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Breathitt 


2 


No 






1 






| 

i 


2 




Itotal 

1 


2 





















210 



DISTRICT 7 — Kentucky 



SEAM Barren Fork 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 

_ , rail MUUtign r«uai bAuawuuii .. .. 

No. Popular Do Not 

County RO> Process StF P&W O.E. O.L. Other o.L. Split Other Pillar Other Information 



SEAM Hazard No. 4 A 



OTHER NAMES Walnut Mountain 



County 


No. 
RCP 


Most 
Popular 
Process 


SSF 


Full 
PSW 


extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Clay 


1 


See Note 








| 1 

1 










Diagonal Splitting; 
Remote Control 


TOTAL 


1 

























211 



DISTRICT 7 - Tennessee 



SEAM r^-^n 


No. 
RCP 


Most 
Popular 
Process 


OTHER NAI 

Full 
S6F PSW 


4ES 


















County 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other 


Information 1 


Anderson 


30 


No 


5 












5 


1 


24 




Campbell 


14 


No 






! 










14 




Scott 


3 


NO 






i 
i 










3 




Morgan 


1 


Z.D. 


1 












1 








TOTAL 


48 



























SEAM Jellico 


Most 

Popular 
Process 


OTHER NAI 

Full 
S£F PSW 


<ES Harlan. Lower Elkhorn 










No. 

County RCP 


Extraction Partial Extraction 
O.E. O.L. Other O.L. Split Other 


Do Not 
Pillar 


Other Information 


Campbell 


22 


No 


















22 




Claiborne 


8 


No 


1 


1 


1 






1 


6 




Anderson 


7 


No 






i 

I 










7 




Scott 


5 


No 






1 
1 










5 




Morgan 


1 


No 


















1 




TOTAL 


43 

























SEAM Sewanee 


Most 
Popular 

Process 


OTHER NAI 

Full 
S&F PSW 


tES Lantana, 


Mary Lee. Sewell 








NO. 

County RCP 


Extraction 
O.E. O.L. 


Partial Extraction 
Other O.L. Split Other 


00 Not 
Pillar 


Other Information 


Marion 


18 


No 


1 




3 








4 




13 




Sequatchie 


6 


No 


















6 




Grundy 


2 


I.D. 






1 








1 




1 




Hamilton 


2 


No 


















2 




Bledsoe 


1 


No 


















1 




TOTAL 


29 























212 



DISTRICT 7 - Tennessee 



SEAM Walnut Mountain 


OTHER NAI 

Full 
SfcF PtW 


<ES Red Ash 














Most 
No. Popular 
County RCP Process 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Anderson 


14 


NO 


2 












4 




10 




Campbell 


5 


No 


















5 




Marion 


2 


No 


















2 




Scott 


2 


No 


















2 




Morgan 


1 


NO 


















1 


i 

1 


TOTAL 


24 

























SEAM Rich Mountain 



OTHER NAMES Blue Gem 



County 


No. 
RCP 


Most 
Popular 
Process 


Sfcf 


Full 
PSW 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Campbell 


16 


No 








i 

1 








16 




Anderson 


1 


NO 






I ! 








1 




Claiborne 


1 


NO 






! j 








1 




TOTAL 


18 










1 











SEAM Glen. Mary 


Most 
Popular 
Process 


OTHER NAI 

Full 
SfcF PtW 


'ffiS Ponlar. Porilar Creek. Horse Creek 






No. 

County RCP 


Extraction Partial Extraction 
O.E. O.L. Other O.L. Split Other 


Do Not 
Pillar 


Other Information 


Scott 


6 


No 








1 








6 




Anderson 


2 


No 








| 








2 




TOTAL 

1 


8 























SEAM Jovner 


Most 

Popular 
Process 


OTHER NAI 

Full 
SfcF P&W 


1ES PIVhnrn il . »l m » 












No. 

County RCP 


Extraction 
O.E. O.L. Other 


Partial Extraction 
O.L. Split Other 


Do Not 

Pillar 


Other Information 


Anderson 


7 


No 


















7 




Campbell 


1 


No 






i 








1 


J 


TOTAL 


8 

























213 



DISTRICT 7 - Tennessee 



SEAM Rex 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 

No. Popular —.-. — ---.. -— -.-- Do Not 

County RCP Process S6F PSW O.E. O.L. Other O.L. Split Other Pillar Other Information 



T 



Claiborne 



NO 



Campbell 



SEAM Piedmont 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 

No. Popular "'"'"' :,-■.»-. ._„,.. ^ Not 

County RCP Process SSF PtW O.E. O.L. Other O.L. Split Other Pillar Other Information 



Anderson 



No 



m 



SEAM Coal 


Creek 

No. 

RCP 


Most 
Popular 
Process 


OTHER NAI 

Full 
SfcF PSW 


<ES 












County 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Anderson 


3 


No 






' i ■ ■ 

! i 




| 


3 




Campbell 


1 


NO 






! 1 




i 
1 


1 




Morgan 


1 


NO 






j 






1 
1 


1 




TOTAL 


5 





















SEAM PeeWee 



OTHER NAMES 



County 


No. 

RCP 


Most 
Popular 
Process 


SfiF 


Full 
PfiW 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Campbell 


2 


No 


















2 




Anderson 


1 


P.S. 














1 








Morgan 


1 


NO 


















1 


! 


TOTAL 


4 

























SEAM High Splint 



OTHER NAMES Red Spring. Lower Kittanning 



Full Extraction 



Partial Extraction 



Most 

No. Popular ~"~'" "" ..-..---- • Do Not 

County RCP Process StF PSW O.E. O.L. Other O.L. Split Other Pillar Other Information 



Campbell 



No 



m 



214 



DISTRICT 7 - Tennessee 



SEAM Nelson 



OTHER NAMES 



County 


No. 

RCP 


Most 
Popular 
Process 


S&f 


Full 
PCW 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


DO Not 
Pillar 


Other Information 


Morgan 


2 


No 


















2 




Rhea 


1 


No 


















1 




TOTAL 


3 












l 















SEAM Richland 


Most 
Popular 
Process 


OTHER NX 

Full 
SSF PfiW 


«ES Blue Creek 












No. 

County RCP 


Extraction 

O.E. O.L. Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Rhea 


2 


No 
















2 




Hamilton 


1 


No 


















1 




TOTAL 


3 

























SEAM Wilder 



OTHER NAMES 



County 


No. 

RCP 


Most 
Popular 
Process 


S£F 


Full 
PfiW 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
. Split Other 


Do Not 
Pillar 


Other Information 


Fentress 


1 


No 


















1 




Overton 


1 


P.S. 














1 








Putman 


1 


No 


















1 




TOTAL 


3 























SEAM Block 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular Do Not 

County RCP Process SfcF PfiW O.E. O.L. Other o.L. Split Other Pillar Other Information 



m 



Anderson 



SEAM Murray 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular Do Not 

County RCP Process SfiF PfiW o.E. O.L. Other O.L. Split Other Pillar Other Information 



Campbell 



No 



m 



215 



DISTRICT 7 - Tennessee 

SEAM Peabody OTHER NAMES 



County 


No. 
RCP 


MOSt 

Popular 
Process 


sir 


Full 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


DO Not 

Pillar 


Other Information 


Campbell 


2 


'- II 


r ' 






1 




n i 


1 

! TOTAL 


2 























SEAM Brimstone 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 

No. Popular " * " -"""—•• ...— .—. — ._—... do Rot 

County RCP Process S*F PtW O.E. O.L. Other O.L. Split Other Pillar Other Information 



Scott 



No 



GJ 



TOTAL 



SEAM Jordon 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular """ —--_—.-... do Not 

County RCP Process S4F PCH O.E. O.L. Other O.L. Split Other Pillar Other Information 



Campbell 



NO 



m 



TOTAL 



216 



DISTRICT 8 - Illinois and Indiana 



SEAM Illinois »6 


OTHER NAf 

Full I 
S&F PSW 


1ES Grade Creek «5, H 


i-rrin 










No. 
County RCP 


Most 
Popular 
Process 


Extraction 
O.E. O.L. Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


i 

1 Franklin 


5 


SSF 


4 
















•1 


'Longwall 


I Jefferson 


3 


S6F 


3 






! 


1 










j Randolph 


3 


No 












1 






2 




Douglas 

1. . . 


2 


No 


















2 




i 
[Macoupin 


2 


No 


















2 




i 
'Williamson 


2 


S&F 
No 


1 
















1 




1 Christian 


1 


No 


















1 




Clinton 


1 


NO 


















1 




Montgomery 


1 


P.O. 












1 






! 




1st. Clair 

I 


1 


P.O. 












1 










IVermillian 


1 


NO 


















1 




! 


1 

























IJJ 



SEAM Illinois #5 


OTHER NAI 

Full 
SSF PSW 


1ES 
















Most 
No. Popular 
County RCP Process 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Saline 


2 


P.O. 






I ! 


2 










Williamson 


2 


Nc 


















2 




Wabash 


1 


P.O. 








! 


1 










TOTAL 


5 

- ■■ •■ 

























SEAM Indiana #5 




OTHER NAI 

Full 
SfcF PCW 


4ES 
















No. 

County RCP 


Most 

Popular 
Process 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Greene 


1 


No 


I 
| 














1 




Pike 


1 


No 






1 

1 










1 




Warrick 


1 


No 


















1 




TOTAL 


3 

























217 






DISTRICT 8 



SEAM Indiana UG 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Host 
. No. Popular """ Do Not 

County RCP Process StF PSW o.E. O.L. Other o.L. Split Other Pillar Other Information 



-r 



m 



! TOTAL 



218 



DISTRICT 8 - Ohio 



5EAM FlttSburqh 


#8 

Most 

Popular 
Process 


OTHER NAI 
Full 


1ES 


















No. 
County RCP 


Extraction 
O.E. Q.L. 


Other 


Partial Extraction 

O.L. Split Other 


Do Not 
Pillar 


Other Information 




Belmont 


6 


P.O. 


i 
1 


I j 


6 












Harrison 


2 


P.O. 


i 




I 


2 












iMonroe 


2 


P.O. 


| 


I 


2 












Itotal 


10 

























OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 

„ . lUii caul outrun raii*i.a± LAuiuLiiuii 

. No. Popular Do Not 

County RCP Process S&F PfcW O.E. O.L. Other O.L. Split Other Pillar Other Information 



Perry 


3 


No 


! ! 1 


! i 


3 




Coshocton 


2 


No 




i i 


i ; 


2 




Muskingum 


1 


No 




1 i 




I 




: 

i TOTAL 


6 















SEAM » 4 * 






OTHER NAMES Clarion 












County 


No. 
RCP 


Most 
Popular 
Process 


Full Extraction 
SSF PSW O.E. O.L. 


Other 


Partial Extraction 
O.L. split Other 


Do Not 
Pillar 


Other Information 


Jackson 


2 


No 




i 




2 


• 


Meigo 


2 


No 


i 


! i 
i 1 


1 




2 




Vinton 


2 


NO 


i 


■ 


! ! 


2 


1 


TOTAL 


6 



















SEAM #6 A 

Most 
. No. Popular 
County RCP Process 


OTHER NAMES Lower Freeciort , Ohio Freeporr 






Full Extraction Partial Extraction 

Do Not 

SSF P4W O.E. O.L. Other O.L. Split Other Pillar Other Information 


Harrison 


4 


P.O. 


i i ] i 


2 j i ; i 






Tuscarawas 


1 


No 


i ! 1 i 


| i 


i 




TOTAL 
1- 


5 













219 






DISTRICT 8 _ Ohio 



SEAM »BA 




OTHER NAMES 






Most 

Full Extraction Partial Extraction __ „ . 
No. Popular Do Not 

County RCP Process S&F PIW o.E. O.L. Other O.L. Split Other Pillar Other Information 


Meigo 


1 


- 1 ! i 1 ! 1 




1 > 1 


TOTAL 


1 









SEAM 7 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 

No. Popular ,,.-, Oo NQt 

County RCP Process S&F P£W o.E. O.L. Other O.L. split Other Pillar Other Information 



Guernsey 



m 



TOTAL 



220 



DISTRICT 9 - Arkansas, Oklahoma 



SEAM Hartshorne 


Most 
Popular 
Process 


> OTHER NAI 

Full 
S&F P&W 


4ES 










No. 
County RCP 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


LeFlore, 
Oklahoma 


3 


No 


1 

1 
1 


1 

i : 


1 ' 


3 




Sebastion 
Arkansas 


1 


No 


1 1 i 1 

i i ! ! 


! ! 
I i 


1 




TOTAL 


4 

















DISTRICT 9 - Iowa 



SEAM Cherokee 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular Do Not 

County RCP Process S&F P&W O.E. O.L. Other O.L. Split Other Pillar Other Information 



I TOTAL 



NO 



rn 



DISTRICT 9 - Mew Mexico 



SEAM "ork 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
. No. Popular Do Not 

County RCP Process S&F Ptw o.E. O.L. Other o.L. Split Other Pillar Other Information I 



1 Colfax 



S&F 



nn 



DISTRICT 9 - Wyoming 



SEAM Bed SO 



OTHER NAMES 



MOSt 

. No. Popular 
County RCP Process 


S&F 


Full Extraction Partial Extraction _ „ 

so Not 

P&w O.E. O.L. Other o.L. Split Other Pillar Other Information 


Carbon 


1 


NO 




i II 




TOTAL 


1 













221 






DISTRICT 9 - Wyoming 



SEAM Rock Springs * 3 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular '" -«--------■ .. ,.-,..,. ^ NQt 

County RCP Process SfcF PSW O.E. O.L. Other O.L. Split Other Pillar Other Information 



Sweetwater 



Outside Lj fts on Diamond 
Diamond Pillars 



222 



DISTRICT 9 - Colorado 



SEAM B 






OTHER NAJ 

Full 
S&F P&W 


1ES 
















County 


No. 
RCP 


Most 
Popular 
Process 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Pitkin 


4 


S&F 
No 


2 
















2 




Gunnison 


2 


S&F 
No 


1 
















1 




TOTAL 


6 





















SEAM E 






OTHER NAI 

Full 
S&F PCW 


IBS 














County 


No. 

RCP 


MOSt 

Popular 
Process 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
o.l. Split Other 


Do Not 
Pillar 


Other Information 


Delta 


2 


S&F 
No 


1 




1 

| 1 








1 




Gunnison 


2 


S&F 


2 




1 i 












larfield 


1 


NO 






1 ! 








1 




1 

;■ ror^L 


. 5 























SEAM Cameo 



Most 
No. Popular 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Do Not 



County RCP Process S&F P&W O.K. O.L. Other O.L. Split Other Pillar Other Information 



m 



SEAM C 



OTHER NAMES Juanita 



Full Extraction 



Partial Extraction 



Most 
No. Popular *.,.-- ......... ^ N<jt 

County RCP Process S&F P&W O.E. O.L. Other O.L. Split Other Pillar Other Information 



S&F 
No 




223 



DISTRICT 9 - Colorado 

SEAM D OTHER NAMES 



County 


No. 

RCP 


MO»t 
Popular 
Process 


Stf 


Full 
P£W 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
°' L ' Split Other 


Do Not 
Pillar 


Other Information 


Carfield 


1 


NO 


















1 




Delta 


1 


SSF 


1 




















TOTAL 


2 

























SEAM _F 



OTHER NAMES 



County 


No. 
RCP 


Most 
Popular 
Process 


S6F 


Full 
P&W 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Gunnison 


2 


P.S. 
No 














1 




1 




| TOTAL 


2 

























SEAM A 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular —— ._.—__ _. ______ Do Not 

County RCP Process StF PftW O.E. O.L. Other O.L. Split Other Pillar Other Information 



Pitkin 



No 



na 



SEAM Allen 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular ' ~* ——.—■—' • - — ----- oo Not 

County RCP Process SsF PtM O.E. O.L. Other O.L. Split Other Pillar Other Information 



m 



Los Animas 



! TOTAL 



SSF 



SEAM Anderson 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 

No. Popular " " -— • ._.„_. _„..„.„.. oo Not 

County RCP Process StF PSH o.E. O.L. Other O.L. Split Other Pillar Other Information 



T 



Pitxin 



No 



HJ 



224 



DISTRICT 9 - Colorado 

SEAM Apache OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 

_ . lull LALtoction raitiai tAwituwii 

No. Popular Do Not 

County RCP Process StF PSW O.E. O.L. Other O.L. Split Other Pillar Other Information 



i Las Animas 



T 



in 



SEAM Brook side 



OTHER NAMES 



County 


No. 

RCP 


Most 

Popular 
Process 


S&F 


Full 

PIW 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. split Other 


Do Not 
Pillar 


Other Information 


Fremont 


1 


No 






! ! 1 


! 1 . 




TOTAL 


1 





















SEAM Laramie #3 



OTHER NAMES 



County 


No. 
RCP 


Most 

Popular 
Process 


S&F 


Full Extraction 
PAW O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other 


Infonration 


Weld 


1 


I.D. 


1 


! i 
i 


1 


1 1 ' i 


1 






j TOTAL 


1 



















SEAM Lower Starkville 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular Do Not 

County RCP Process S&F PtW O.E. O.L. Other O.L. Split Other Pillar Other Information 



Los Animas 



No 



m 



SEAM Pinnacle 



OTHER NAMES 



Most 
No. Popular — --- ----- .. ^ NQt 



Full Extraction 



Partial Extraction 



County 


RCP 


Process 


StF 


PtW 


O.E. 


O.L. 


Other 


O.L. 


Split 


Other 


Pillar 


Other Information 


Routt 


1 


,., 


M 








1 

1 




I i 


1 


TOTAL 


1 

























225 



DISTRICT 9 - Colorado 



SEAM Pueblo 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular °° Not 

County RCF Process StF P6W O.E. O.L. Other O.L. Split Other Pillar Other Information 



LaPlata 



iZI 



TOTAL 



SEAM Sunny Ridge 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular Do Not 

County RCP Process StF PSW O.E. O.L. Other O.L. Split Other Pillar Other Information 



I Garfield 



No 



m 



I TOTAL 



SEAM Wade 






OTHER NA1 

Full 
SiF PtW 


1ES 














County 


No. 
RCP 


Most 
Popular 
Process 


Extraction 
O.E. O.L. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


, Routt 


1 


No 




1 

j 










1 




! 

TOTAL 


1 























SEAM Wattis 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular Do Not 

County RCP Process StF PCH O.E. O.L. Other O.L. Split Other Pillar Other Information 



I Carbon 



I.D. 



I 



EH 



226 



DISTRICT 9 - Utah 



seam Hiawatha 




OTHER NAMES 












No. 

County RCP 


Host 
Popular 
Process 


Full Extraction 
S&F PtW O.E. 0.1.. 


Other 


Partial Extraction 
O.L. Split Other 


Do Not 
Pillar 


Other Information 


Emery 


3 


P.S. 


■ iil! 




i 

2 


1 




Carbon 


2 


I.D. 


■1 1 - 1 


1 


1 i 






Sevier 


1 


P.S. 


1 ! i ! 


' ■ ! 






TCTAL 


6 

















SEAM Blind Canyon 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular Do Not 

County RCP Process S&F PiW O.E. O.L. Other o.L. Split Other Pillar Other Information 



T 



T 



EH 



| Emery 



T 



S&F 



SEAM Sunnvside 



OTHER NAMES 



Most 

. Full Extraction Partial Extraction 
No. Popular Do Not 

County RCP Process S&F PtW O.E. O.L. Other O.L. Split Other Pillar Other Information 


Carbon 


3 


S&F 


1 

3 | ; 1 










Emery 


1 


I.D. 


1 ! 1 i ; 


I > ! 






TOTAL 


4 















OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular " Do Not 

County RCP Process SSF P&W O.E. O.L. Other O.L. Split Other Pillar Other Information 



Carbon 


1 


I.D. 


1 ' ! ! 
1 I ! : i 




1 ! 




i 


Grand 


1 


No 


1 I 




i 


i 


i 


Kane 


1 


I.D. 


1 i ; : ! 


i * 


i 


1 


TOTAL 


3 















227 



DISTRICT 9 - Utah 



SEAM Rock Canyon 



OTHER NAMES 



Full Extraction 



Partial Extraction 



MOSt 
No. Popular ~" " "*'" """" Do Not 

County RCP Process S*F PtW O.E. O.L. Other O.L. Split Other Pillar Other Infornatior. 



-r 



SEAM Sur.seain «3 



OTHER NAMES 



Full Extraction 



Partial Extraction 



Most 
No. Popular - . .._-.._._... ^ Nqc 

County RCP Process StF PtW O.E. O.L. Other O.L. Split Other Pillar Other Information 



Carbon 



•1 



E3 



Bump Control Cuts 



228 



*U S GOVERNMENT PRINTING OFFICE: 1981 350«048/8560 



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